[Federal Register Volume 75, Number 81 (Wednesday, April 28, 2010)]
[Proposed Rules]
[Pages 22439-22468]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-9603]



[[Page 22439]]

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Part II





Environmental Protection Agency





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40 CFR Part 87



Advance Notice of Proposed Rulemaking on Lead Emissions From Piston-
Engine Aircraft Using Leaded Aviation Gasoline; Proposed Rule

Federal Register / Vol. 75 , No. 81 / Wednesday, April 28, 2010 / 
Proposed Rules

[[Page 22440]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 87

[EPA-HQ-OAR-2007-0294; FRL-9141-7]
RIN 2060-AP79


Advance Notice of Proposed Rulemaking on Lead Emissions From 
Piston-Engine Aircraft Using Leaded Aviation Gasoline

AGENCY: Environmental Protection Agency (EPA).

ACTION: Advance notice of proposed rulemaking.

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SUMMARY: EPA is issuing this Advance Notice of Proposed Rulemaking 
(ANPR) to describe information currently available and information 
being collected that will be used by the Administrator to issue a 
subsequent proposal regarding whether, in the Administrator's judgment, 
aircraft lead emissions from aircraft using leaded aviation gasoline 
(avgas) cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health or welfare. In this ANPR we 
describe and request comment on the data available for evaluating lead 
emissions, ambient concentrations and potential exposure to lead from 
the continued use of leaded avgas in piston-engine powered aircraft. We 
also describe and request comment on additional information being 
collected that will inform any future action.
    This ANPR is being issued to further respond to a petition 
submitted by Friends of the Earth (FOE) in 2006. Emissions of lead from 
piston-engine aircraft using leaded avgas comprise approximately half 
of the national inventory of lead emitted to air. There are almost 
20,000 airport facilities in the U.S. at which leaded avgas may be 
used. EPA has long-standing concerns regarding exposure to lead, 
particularly during childhood. The most recent review and revision of 
the National Ambient Air Quality Standard (NAAQS) for lead, promulgated 
in 2008, found that serious health effects occur at much lower levels 
of lead in blood than previously identified and did not identify a safe 
level of lead exposure.

DATES: Comments must be received on or before June 28, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2007-0294, by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-9744.
     Mail: Environmental Protection Agency, Mail Code: 6102T, 
1200 Pennsylvania Ave., NW., Washington, DC 20460. Please include two 
copies.
     Hand Delivery: EPA Docket Center (Air Docket), U.S. 
Environmental Protection Agency, EPA West Building, 1301 Constitution 
Avenue, NW., Room: 3334 Mail Code: 2822T, Washington, DC. Such 
deliveries are only accepted during the Docket's normal hours of 
operation, and special arrangements should be made for deliveries of 
boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2007-0294. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
http://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through http://www.regulations.gov your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the EPA Docket Center, 
EPA/DC, EPA West, Room 3334, 1301 Constitution Avenue, NW., Washington, 
DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Marion Hoyer, Assessment and Standards 
Division, Office of Transportation and Air Quality, 2000 Traverwood 
Drive, Ann Arbor, MI 48105; telephone number: (734) 214-4513; fax 
number: (734) 214-4821; e-mail address: hoyer.marion@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. What should I consider as I prepare my comments for EPA?

    1. Submitting CBI. Do not submit this information to EPA through 
http://www.regulations.gov or e-mail. Clearly mark the part or all of 
the information that you claim to be CBI. For CBI information in a disk 
or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM 
as CBI and then identify electronically within the disk or CD ROM the 
specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR Part 2.
    2. Tips for Preparing Your Comments. When submitting comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register date and 
page number).
     Follow directions--The agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree, suggest alternatives, 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.

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     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the comment period 
deadline identified.

Table of Contents

I. Overview
    A. Background on Leaded Aviation Gasoline
    B. Background Information Regarding General Aviation and Use of 
Piston-Engine Aircraft
    C. Background on the Petition and EPA's Response
    D. Statutory Authority
    1. Background
    2. Regulatory Authority for Emission Standards
    3. Regulatory Authority for Fuel Standards
    E. Federal Actions To Reduce Lead Exposure
II. Health and Welfare Effects of Lead
    A. Multimedia and Multi-Pathway Exposure Considerations
    B. Health Effects Information
    1. Blood Lead
    2. Health Effects
    3. At-Risk Populations and Life Stages
    C. Welfare Effects
    1. Terrestrial Ecosystems
    2. Aquatic Ecosystems
III. Lead Emissions from Piston-Engine Aircraft
    A. Inventory of Lead from Piston-Engine Powered Aircraft
    1. National Emissions of Lead from Piston-Engine Aircraft
    2. Airport-Specific Emissions of Lead from Piston-Engine 
Aircraft
    B. Projections for Future Growth
IV. Lead Concentrations in the Vicinity of Airports
    A. Chemical and Physical Properties of Lead Emitted by Piston-
Engine Aircraft
    B. Summary of Airport Lead Monitoring and Modeling Studies
    1. Summary of Airport Lead Monitoring Studies
    2. Summary of Airport Lead Modeling Studies
V. Exposure to Lead from Piston-Engine Aircraft and Potential for 
Impacts
    A. Exposure to Lead Emissions from Piston-Engine Aircraft
    1. Population Residing Near Airports
    2. Children Attending School Near Airports
    3. Agricultural Activities
    4. Pilots, Student-Trainees, Passengers
    5. Bioaccumulation of Lead in Aquatic Organisms
    B. Related Exposures of Concern
    1. Lead Contribution to Ambient Particulate Matter
    2. Ethylene Dibromide
    3. Non-Exhaust Exposure to Tetraethyl Lead
VI. Additional Information Available for the NPRM to Evaluate the 
Potential for Public Health and Welfare Impacts and Considerations 
Regarding Engine Emission Standards
    A. The Lead NAAQS and Lead Emissions from Piston-Engine Aircraft
    1. Monitoring Lead at Airports to Evaluate Ambient 
Concentrations to Which Lead Emissions from Piston-Engine Aircraft 
Contribute
    2. Evaluating the Contribution of Lead Emissions from Piston-
Engine Aircraft to Areas Approaching or Exceeding the Lead NAAQS
    B. Additional Information EPA Is Collecting to Evaluate Ambient 
Lead Concentrations Attributable to Emissions from Piston-Engine 
Aircraft
    C. Considerations Regarding Engine Emission Standards
VII. Statutory and Executive Order Reviews

I. Overview

    EPA is publishing this ANPR in further response to a petition 
submitted by Friends of the Earth (FOE) entitled ``Petition for 
Rulemaking Seeking the Regulation of Lead Emissions From General 
Aviation Aircraft Under Sec.  231 of the Clean Air Act.'' \1\ In the 
petition, FOE requests that the Administrator of EPA: (1) Make a 
finding that lead emissions from general aviation aircraft endanger 
public health and welfare and issue a proposed emission standard for 
lead from general aviation aircraft under the Clean Air Act (CAA) or, 
alternatively, (2) if the Administrator of EPA believes that 
insufficient information exists to make such a finding, commence a 
study and investigation of the health and environmental impacts of lead 
emissions from general aviation aircraft, including impacts to humans, 
animals and ecosystems under the CAA and issue a public report on the 
findings of the study and investigation. Section I.C of this notice 
discusses the background on the petition and EPA's response to date and 
Section I.D discusses EPA's statutory authority under section 231(a) of 
the CAA. Under the CAA, if, in the Administrator's judgment, lead 
emissions from the use of leaded avgas cause or contribute to air 
pollution which may reasonably be anticipated to endanger public health 
or welfare, then EPA would be required under our statutory authority to 
prescribe standards to control the emissions of lead from piston-engine 
aircraft. In promulgating such standards, the EPA would be required to 
consult with the Federal Aviation Administration (FAA), and could not 
change standards if doing so would significantly increase noise and 
adversely affect safety. FAA would then be required, after consultation 
with EPA, to prescribe regulations to insure compliance with any 
standards to control the emissions of lead from piston-engine aircraft. 
Under 49 U.S.C. 44714, FAA would also be required to prescribe 
standards for the composition or chemical or physical properties of 
piston-engine fuel or fuel additives to control or eliminate aircraft 
lead emissions.
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    \1\ See docket item EPA-HQ-OAR-2007-0294-0003.
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    In this notice, we discuss our analysis of the relevant information 
and issues to date, and we seek further public input regarding FOE's 
petition. For the purposes of this notice, we will refer to the 
positive or negative exercise of judgment as to whether lead emissions 
from aircraft engines resulting from the use of aviation gasoline 
(avgas) cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health or welfare as the ``endangerment 
finding'' and the ``cause or contribute finding.'' This short-hand use 
of ``endangerment finding'' and ``cause or contribute finding'' is 
strictly for purposes of simplifying the discussion, and should not be 
read as implying that EPA considers the exercise of the Administrator's 
judgment to require a formal ``finding'' or ``determination.''
    In 2006, EPA completed the Air Quality Criteria Document (AQCD) for 
Lead, which critically assesses and integrates relevant scientific 
information regarding the health effects of lead.\2\ EPA concluded that 
the latest evidence indicates adverse health effects, most notably 
among children, are occurring at much lower levels than previously 
considered. In 2008, EPA decreased the level of the primary National 
Ambient Air Quality Standard (NAAQS) for lead from 1.5 micrograms per 
cubic meter ([mu]g/m\3\) to 0.15 [mu]g/m\3\ in order to provide 
increased protection for children and other at-risk populations against 
an array of adverse health effects, most notably neurological effects 
in children, including neurocognitive and neurobehavioral effects.\3\ 
Neurotoxic effects in children and cardiovascular effects in adults are 
among those best substantiated as occurring at blood lead 
concentrations as low as 5 to 10 [mu]g/dL (or possibly lower); and 
these categories are currently clearly of greatest public health 
concern (AQCD for Lead, p. 8-60). The U.S. Centers for Disease Control 
and Prevention (CDC) concluded in 2005 that no ``safe'' threshold for 
blood lead has been identified, and emphasized the

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importance of preventative measures.4 5 To provide increased 
protection against lead-related welfare effects, in 2008 EPA revised 
the secondary standard to be identical in all respects to the revised 
primary standard. Section II of this ANPR provides more detail 
regarding health and welfare effects of lead.
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    \2\ U.S. Environmental Protection Agency (2006) Air Quality 
Criteria for Lead. Washington, DC, EPA/600/R-5/144aF. Available 
online at: http://www.epa.gov/ncea/.
    \3\ National Ambient Air Quality Standards for Lead 73 FR 66965 
(Nov. 12, 2008).
    \4\ Centers for Disease Control and Prevention (2005) Preventing 
lead poisoning in young children: a statement by the Centers for 
Disease Control and Prevention. Atlanta, GA: U.S. Department of 
Health and Human Services, Public Health Service. August.
    \5\ Advisory Committee on Childhood Lead Poisoning Prevention 
(ACCLPP) (2007) Interpreting and managing blood lead levels <10 ug/
dL in children and reducing childhood exposures to lead: 
Recommendations of CDC's Advisory Committee on Childhood Lead 
Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR-
8). November 2, 2007.
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    Given the recent findings of the science summarized by EPA in the 
AQCD for Lead as well as the findings of the CDC, the Agency is 
concerned about the potential for health and welfare effects from 
exposure to lead emissions from aircraft engines using leaded avgas. On 
a national basis, emissions of lead from aircraft engines using leaded 
avgas are the largest single source category for emissions of lead to 
air, comprising approximately half of the national inventory.\6\ There 
are almost 20,000 airport facilities in the U.S. at which leaded avgas 
may be used, and in some areas of the country there are densely 
populated residential developments immediately adjacent to these 
airport facilities. As described in Section V, we estimate that up to 
16 million people reside and three million children attend school in 
close proximity to airport facilities servicing piston-engine aircraft 
that are operating on leaded avgas.
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    \6\ U.S. Environmental Protection Agency Electronic Report on 
the Environment. Available at: http://cfpub.epa.gov/eroe. Updated in 
December 2009 using the 2005 National Emissions Inventory.
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    Exposure to lead occurs through multiple routes (e.g., inhalation, 
ingestion and dermal adsorption), and lead emitted to the atmosphere 
can contribute to lead levels in multiple media (e.g., air, soil and 
water). The lead monitoring studies conducted at or near airports, 
described in Section IV of this ANPR, indicate that lead levels in 
ambient air on and near airports servicing piston-engine aircraft are 
higher than lead levels in areas not directly influenced by a lead 
source. In addition, the emissions of lead from these engines are also 
expected to distribute widely through the environment. This is in part 
due to the emission of lead at various altitudes during aircraft 
operations as well as the fine particle size of lead emitted by piston 
engines. Continued use of leaded avgas provides an ongoing source of 
new lead that is deposited in various environmental media and 
participates in long term cycling mechanisms in the environment, thus 
adding to the pool of lead available for uptake by humans and biota. We 
expect the lead from avgas to be bioavailable in the same way as the 
lead emitted by motor vehicles in the past, which was well documented 
to contribute to blood levels through both ingestion and inhalation.
    As noted in Section II of this ANPR, once deposited to surfaces, 
lead can subsequently be resuspended into the ambient air and, because 
of the persistence of lead, emissions of this metal contribute to 
environmental media concentrations for many years into the future. Lead 
that is a soil or dust contaminant today may have been airborne 
yesterday or many years ago. Therefore lead emissions from piston-
engine aircraft could contribute to increased lead exposure and risk 
currently or at some time in the future.
    Section VI of this ANPR provides an overview of additional 
information that will be available for the NPRM to evaluate the 
potential for public health and welfare impacts from lead emitted by 
piston-engine aircraft. These additional data will come from lead 
monitoring being planned to satisfy requirements of the Lead NAAQS, air 
quality modeling planned at EPA and any information submitted to EPA 
during the comment period for this ANPR.
    The remainder of this section provides background on leaded avgas, 
FOE's petition and EPA's response to the petition to date, and 
statutory authority over emissions, fuel for aircraft and Federal 
actions to reduce lead exposure. Section II provides a discussion of 
the health and welfare effects of lead. Sections III, IV and V describe 
the emissions of lead from avgas, ambient lead concentration in the 
vicinity of airports and potential exposure to lead from leaded avgas, 
respectively. In Section VI, we describe the additional information EPA 
is collecting and considerations regarding engine emission standards. 
Section VII contains information on statutory and executive order 
reviews covering this action.

A. Background on Leaded Aviation Gasoline

    In 1996, EPA promulgated regulations that banned the use of leaded 
gasoline in highway vehicles.\7\ The addition of lead to fuel used in 
piston-engine powered aircraft was not banned in this action, and the 
use of leaded avgas is the largest remaining source category of lead 
emissions. Lead is not added to jet fuel that is used in commercial 
aircraft, most military aircraft, or other turbine-engine powered 
aircraft. Most piston-engine aircraft fall into the categories of 
either general aviation (GA) or air taxi (AT). GA and AT aircraft 
include a diverse set of aircraft types and engine models and are used 
in a wide variety of applications.\8\
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    \7\ See ``Prohibition on Gasoline Containing Lead or Lead 
Additives for Highway Use'' 61 FR 3832 (Feb. 2, 1996).
    \8\ Commercial aircraft include those used for scheduled service 
transporting passengers, freight, or both. Air taxis fly scheduled 
and for-hire service carrying passengers, freight or both, but they 
usually are smaller aircraft than those operated by commercial air 
carriers. General aviation includes most other aircraft (fixed and 
rotary wing) used for recreational flying, business, and personal 
transportation.
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    Lead is added to fuel for piston-engine aircraft in the form of 
tetraethyl lead (TEL). This lead additive helps boost fuel octane, 
prevents knock, and prevents valve seat recession and subsequent loss 
of compression for engines without hardened valves. There are two main 
types of leaded avgas: 100 Octane, which can contain up to 4.24 grams 
of lead per gallon; and 100 Octane Low Lead (100 LL), which can contain 
up to 2.12 grams of lead per gallon. Currently, 100LL is the most 
commonly available and most commonly used type of avgas.9 10 
TEL was first used in piston-engine aircraft in 1927.\11\ Into the 
1950s commercial and military aircraft in the U.S. operated on 100 
Octane leaded avgas, but in subsequent years, the commercial and 
military aircraft fleet largely converted to jet turbine-engine 
propelled aircraft. However, the use of avgas containing 4 grams of 
lead per gallon continued in piston-engine aircraft until the early 
1970s when 100LL became the dominant leaded fuel in use. Currently, 
very little 100 Octane is supplied in the U.S. and we use the lead 
content of 100LL (2.12 grams per gallon) to characterize the lead 
available from avgas.
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    \9\ ChevronTexaco (2006) Aviation Fuels Technical Review. FTR-3. 
Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
    \10\ ASTM International (2007) Standard Specification for 
Aviation Gasolines D910-06.
    \11\ Ogston, A.R. (1981) A Short History of Aviation Gasoline 
Development, 1903-1980. Society of Automotive Engineers. Paper 
number 810848.
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    Since lead is a persistent pollutant, it is important to 
characterize the historical use of this fuel.

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Approximately 14.6 billion gallons of leaded avgas have been consumed 
in the U.S. between 1970 and 2007. If this fuel was all 100LL, it would 
account for approximately 34,000 tons \12\ of lead emitted to the 
air.\13\ In terms of the potential impacts from long-term use of leaded 
avgas at and near airports, older facilities would be expected to have 
a legacy of lead, particularly those that supported military and 
commercial aircraft operating on 100 Octane. Over 3,000 of the 20,000 
airport facilities in the U.S. are at least 50 years old and some 
airports have been in operation since the early 1900s.
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    \12\ In this ANPR and in EPA's National Emissions Inventory, the 
use of the unit tons refers to short tons.
    \13\ Oak Ridge National Laboratory (2009) Transportation Energy 
Data Book: Edition 28. Available at: http://cta.ornl.gov/data. Table 
A.7.
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    The Department of Energy's (DOE's) Energy Information 
Administration (EIA) provides information on the volume of leaded avgas 
supplied in the U.S.\14\ The Department of Transportation's (DOT's) FAA 
provides information on the volume of leaded avgas consumed in the 
U.S.\15\ EPA has historically used the DOE EIA avgas fuel volumes 
supplied to calculate national lead inventories from the consumption of 
leaded avgas. We are currently evaluating methods used by DOE and DOT 
to calculate annual avgas supply and consumption volumes. In this 
document, we provide avgas fuel volume data supplied by DOE and DOT and 
we note the source of the data for clarity. Over the past ten years, 
DOE estimates of the volume of leaded avgas supplied has ranged from 
326 million gallons in 1999 to 235 million gallons in 2008 (Figure 1). 
Applying the concentration of lead in 100LL (2.12 grams of lead per 
gallon), the total quantity of lead supplied in avgas in the nation has 
ranged from 762 tons in 1999 to 550 tons in 2008 (a 28% decrease over 
that time period). The decrease in fuel consumption is attributed to 
the decrease in piston-engine aircraft activity over that time period 
and not due to a shift to unleaded fuel. There are currently over 
200,000 piston-engine aircraft in the U.S. that continue to consume 
leaded avgas and approximately 2,000 new piston-engine aircraft 
requiring leaded avgas are manufactured annually.\16\ As described in 
Section III.B of this ANPR, there is a slight growth in the activity of 
general aviation aircraft projected to 2025.
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    \14\ Department of Energy Information Administration. Fuel 
production volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm accessed June 2009.
    \15\ U.S. Department of Transportation Federal Aviation 
Administration Aviation Policy and Plans. FAA Aerospace Forecast 
Fiscal Years 2009-2025. p.81. Available at: http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009-2025/media/2009%20Forecast%20Doc.pdf. This document provides historical data 
for 2000-2008 as well as forecast data.
    \16\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook & Industry Outlook. Available online 
at: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
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B. Background Information Regarding General Aviation and Use of Piston-
Engine Aircraft

    In the U.S., general aviation aircraft fly over 27 million hours 
and carry 166 million passengers annually.\17\ Approximately 66 percent 
of hours flown by general aviation are conducted by piston-engine 
aircraft.\18\ Aircraft in the general aviation fleet are used for 
personal transportation (36 percent), instructional flying (19 
percent), corporate uses (11 percent), business (11 percent), air taxi 
and air tours (8 percent) and the remainder include hours spent in 
other applications such as aerial observation and aerial 
application.\19\ According to the 2008 General Aviation Statistical 
Databook & Industry Outlook report by the General Aviation 
Manufacturers Association (GAMA) there were 578,541 pilots in the 
United States in 2008.\20\ According to GAMA, in 2008, the number of 
active single-engine piston-powered aircraft was 144,220 and the number 
of active twin-engine piston-powered aircraft was 18,385. In 2008, 
1,791 new piston-engine aircraft were manufactured in the U.S.
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    \17\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook and Industry Outlook, p.30. Retrieved 
on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
    \18\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook and Industry Outlook, p.30. Retrieved 
on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
    \19\ General Accounting Office Report to Congressional 
Requesters (2001) General Aviation Status of the Industry, Related 
Infrastructure, and Safety Issues. GAO-01-916.
    \20\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook and Industry Outlook, pp.51-55. 
Retrieved on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
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    FAA's Office of Air Traffic provides a complete listing of 
operational airport facilities in the National Airspace System 
Resources (NASR) database.\21\ In 2008, there were 19,896 airport 
facilities in the U.S., the vast majority of which are expected to have 
activity by piston-engine aircraft that operate on leaded avgas. FAA's 
National Plan of Integrated Airport Systems identifies approximately 
3,400 airports that are significant to national air transportation.
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    \21\ An electronic report can be generated from the NASR 
database and is available for download from the Internet at the 
following Web site. http://www.faa.gov/airports_airtraffic/airports/airport_safety/airportdata_5010/. This database is 
updated every 56 days.
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C. Background on the Petition and EPA's Response

    In a 2003 letter to the EPA, FOE initially raised the issue of the 
potential for endangerment caused or contributed to by lead emissions 
from the use of leaded avgas.\22\ In 2006, FOE filed a petition with 
EPA requesting that the Administrator find endangerment or, if there 
was insufficient information to find endangerment, commence a study of 
lead emissions from piston-engine aircraft. In 2007, the EPA issued a 
Federal Register notice on the petition requesting comments and 
information related to a wide range of issues regarding the use of 
leaded avgas and potential public health and welfare exposure 
issues.\23\ We sought comments regarding exposure to lead from avgas 
combustion, emissions of lead, fuel options, and piston-engine 
technology. The comments received to date are publicly available in the 
docket (EPA-HQ-OAR-2007-0294). The majority of comments received 
concerned the nature of the industry and fuel supply issues. The 
commenters did not supply information regarding health or exposure 
issues. In 2008, the EPA initiated a lead study which will improve the 
manner in which EPA models emissions from piston-engine aircraft. This 
study is described in further detail in Section VI of this document. At 
the time we received FOE's petition, the EPA was in the process of a 
full re-evaluation of the science supporting the lead NAAQS. 
Information from that re-evaluation and the relationship between the 
new lead standard and the emissions of lead from piston-engine aircraft 
are discussed in this ANPR.
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    \22\ FOE letter dated December 12, 2003 submitted to EPA Docket 
EPA-HQ-OAR-2002-0030.
    \23\ See ``Petition Requesting Rulemaking To Limit Lead 
Emissions from General Aviation Aircraft; Request for Comments'' 72 
FR 64570 (Nov. 16, 2007).
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D. Statutory Authority

1. Background
    Section 231 of the CAA sets forth EPA's authority to regulate 
aircraft emissions of air pollution. As described further in Section 
I.D.2 of this ANPR, Section 231(a)(2)(A) requires EPA to, from time to 
time, issue proposed emission standards applicable to the emission of 
any air pollutant from any class or classes of aircraft engines which, 
in the Administrator's judgment, cause or contribute to air pollution 
which may reasonably be anticipated to endanger public health or 
welfare. EPA has broad authority in exercising its judgment regarding 
whether emissions from certain sources cause or contribute to air 
pollution which may reasonably be anticipated to endanger public health 
or welfare.\24\ EPA has discussed its ``endangerment finding'' 
authority at length in recent notices for greenhouse gases published in 
the Federal Register, and we refer readers to those notices for 
detailed discussions of the analytical and legal framework.\25\
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    \24\ See, e.g., Ethyl Corp. v. EPA, 541 F.2d 1, 6 (DC Cir.), 
cert. denied 426 U.S. 941 (1976); see also Massachusetts v. EPA, 549 
U.S. 497, 506, n.7 (2007).
    \25\ See, ``Endangerment and Cause or Contribute Findings for 
Greenhouse Gases under Section 202(a) of the Clean Air Act; Final 
Rule,'' 74 FR 66496, 66505 (Dec. 15, 2009); see also, ``Proposed 
Endangerment and Cause or Contribute Findings for Greenhouse Gases 
Under Section 202(a) of the Clean Air Act,'' 74 FR 18886, 18890-94 
(April 24, 2009); see also ``Regulating Greenhouse Gas Emissions 
Under the Clean Air Act; Advance Notice of Proposed Rulemaking,'' 73 
FR 44354, 44421-23 (July 30, 2008).
---------------------------------------------------------------------------

    In 1976, EPA listed lead under CAA section 108, making it what is 
called a ``criteria pollutant.'' As part of the listing decision, EPA 
determined that lead was an air pollutant which, in the Administrator's 
judgment, has an adverse effect on public health or welfare under then 
section 108(a). Once lead was listed, EPA issued primary and secondary 
NAAQS that the Administrator determined were requisite to protect 
public health with an adequate margin of safety and to protect public 
welfare from any known or anticipated adverse effects. Section 
109(b)(1) and (2). As discussed elsewhere in this notice, EPA issued 
the first NAAQS for lead in 1978, and recently revised the lead NAAQS 
by reducing the level of the standard from 1.5 [mu]g/m\3\ to 0.15 
[mu]g/m\3\, measured over a 3-month averaging period. These actions are 
part of the context for the issues before EPA under section 231(a).
    The first part of the endangerment test concerns identification of 
air pollution which may reasonably be anticipated to endanger public 
health or welfare. The CAA defines both ``air pollutant'' and 
``welfare.'' Air pollutant is defined in CAA section 302(g) as: ``Any 
air pollution agent or combination of such agents, including any 
physical, chemical, biological, radioactive (including source material, 
special nuclear material, and byproduct material) substance or matter 
which is emitted into or otherwise enters the ambient air. Such term 
includes any precursors to the formation of any air pollutant, to the 
extent the Administrator has identified such precursor or precursors 
for the particular purpose for which the term `air pollutant' is 
used.'' Lead fits within

[[Page 22445]]

this capacious definition, and has long been regulated as an air 
pollutant by EPA under the CAA (see Section I.E. of this ANPR).
    There is no definition of public health in the CAA. The U.S. 
Supreme Court has discussed the concept in the context of whether costs 
can be considered when setting NAAQS. Whitman v. American Trucking 
Ass'n, 531 U.S. 457 (2001). In Whitman, the Court imbued the term with 
its most natural meaning: ``the health of the public.'' Id., at 466. 
When considering public health, EPA has looked at morbidity, including 
acute and chronic health effects, as well as mortality. EPA has long 
regulated emissions of lead air pollution due to their adverse impacts 
on public health (see section I.E. of this ANPR). Exposure to lead 
causes ``a broad array of deleterious effects on multiple organ 
systems,'' among children and adults (AQCD for Lead, p.8-24 and Section 
8.4.1). Of particular concern are the neurotoxic effects of lead in 
young children.\26\ See Section II of this ANPR for a more complete 
overview of the public health effects of lead.
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    \26\ See ``National Ambient Air Quality Standards for Lead'' 73 
FR 66970-67007 (Nov. 12, 2008).
---------------------------------------------------------------------------

    Regarding ``welfare,'' CAA section 302(h) states that ``[a]ll 
language referring to effects on welfare includes, but is not limited 
to, effects on soils, water, crops, vegetation, man-made materials, 
animals, wildlife, weather, visibility, and climate, damage to and 
deterioration of property, and hazards to transportation, as well as 
effects on economic values and on personal comfort and well-being, 
whether caused by transformation, conversion, or combination with other 
air pollutants.'' This definition is quite broad, and may include 
effects other than those listed here as effects on welfare. Welfare 
effects caused by lead have been evaluated by EPA and were the basis 
for establishing the secondary lead standard.\27\
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    \27\ See ``National Ambient Air Quality Standards for Lead'' 73 
FR 67007-67012 (Nov. 12, 2008).
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    By instructing the Administrator to consider whether emissions of 
an air pollutant cause or contribute to air pollution, the statute is 
clear that she need not find that emissions from any one sector or 
group of sources are the sole or even the major part of an air 
pollution problem. Moreover, section 231(a) does not contain a modifier 
on its use of the term contribute. Unlike some other CAA provisions, it 
does not require ``significant'' contribution.\28\ Congress made it 
clear that the Administrator is to exercise her judgment in determining 
contribution, and authorized regulatory controls to address air 
pollution even if the air pollution problem results from a wide variety 
of sources. The cause or contribute test is designed to authorize EPA 
to identify and then address what may well be many different sectors or 
groups of sources that are each part of an air pollution problem.
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    \28\ See, e.g., CAA sections 111(b); 213(a)(2), (4).
---------------------------------------------------------------------------

    Section 231(a)(2) refers to contribution and does not specify that 
the contribution must be significant before an affirmative finding can 
be made. Any finding of a ``contribution'' requires some threshold to 
be met; a truly trivial or de minimis ``contribution'' might not count 
as such. In the past, the Administrator has evaluated the emissions of 
the source or sources in different ways, based on the particular 
circumstances involved. In some mobile source rulemakings, the 
Administrator has used the percent of emissions from the regulated 
mobile source category compared to the total mobile source inventory 
for that air pollutant as the best way to evaluate contribution.\29\ In 
other instances the Administrator has looked at the percent of 
emissions compared to the total nonattainment area inventory of the air 
pollution at issue.\30\ EPA has found that air pollutant emissions that 
amount to 1.2 percent of the total inventory met the statutory test for 
contribution, triggering EPA's regulatory authority.\31\
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    \29\ See, e.g., 66 FR 5001 (January 18, 2001) (heavy duty engine 
and diesel sulfur rule).
    \30\ See, e.g., 67 FR 68242 (November 8, 2002) (snowmobile 
rule).
    \31\ Bluewater Network v. EPA, 370 F.3d 1, 15 (DC Cir. 2004) 
(For Fairbanks, this contribution was equivalent to 1.2 percent of 
the total daily CO inventory for 2001).
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2. Regulatory Authority for Emission Standards
    Section 231 of the CAA sets forth EPA's authority to regulate 
aircraft emissions of air pollution. Section 231(a)(2)(A) requires EPA 
to, from time to time, issue proposed emission standards applicable to 
the emission of any air pollutant from any class or classes of aircraft 
engines which, in the Administrator's judgment, cause or contribute to 
air pollution which may reasonably be anticipated to endanger public 
health or welfare. Section 231(a)(2)(B)(i) directs EPA to consult with 
FAA on aircraft engine emission standards, and section 231(a)(2)(B)(ii) 
provides that EPA shall not change the aircraft engine emission 
standards if such change would significantly increase noise and 
adversely affect safety. Section 231(a)(3) directs EPA to issue final 
regulations with such modifications as the Administrator ``deems 
appropriate.''
    In setting or revising standards, section 231(b) provides that EPA 
shall have them take effect after such period as EPA finds necessary 
(after consultation with the Secretary of Transportation) to permit the 
development and application of the requisite technology, giving 
appropriate consideration to the cost of compliance within such period. 
Section 231(c) then states that EPA's regulations regarding aircraft 
shall not apply if disapproved by the President, after notice and 
opportunity for public hearing, on the basis of a finding by DOT that 
such regulations would create a hazard to aircraft safety. Section 232 
directs DOT to issue and implement regulations to insure compliance 
with EPA's standards, while section 233 pre-empts States and local 
governments from adopting or enforcing any aircraft emission standards 
that are not identical to EPA's standards.
    In recently reviewing this statutory scheme, the U.S. Court of 
Appeals for the District of Columbia Circuit ruled that it constitutes 
a ``both explicit and extraordinarily broad'' delegation of ``expansive 
authority to EPA to enact appropriate regulations applicable to the 
emissions of air pollutants from aircraft engines.'' \32\
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    \32\ NACAA v. EPA, 489 F.3d 1221, 1229-30 (DC Cir. 2007).
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3. Regulatory Authority for Fuel Standards
    Section 211(c) of the CAA allows EPA to regulate fuels used in 
motor vehicles and nonroad vehicles or engines where emission products 
of the fuel either: (1) Cause or contribute to air pollution that 
reasonably may be anticipated to endanger public health or welfare, or 
(2) will impair to a significant degree the performance of any emission 
control device or system which is in general use, or which the 
Administrator finds has been developed to a point where in a reasonable 
time it will be in general use were such a regulation to be 
promulgated. This section of the CAA was used to eliminate lead from 
fuel used in motor vehicles. EPA's authority to regulate fuels is 
limited to those fuels used in motor vehicles, motor vehicle engines, 
or nonroad engines or vehicles, under CAA section 211(c)(1). The CAA 
defines ``motor vehicle,'' ``nonroad engine,'' and ``nonroad vehicle'' 
in section 216 for purposes of part A of title II of the CAA. Part A is 
also where the authority to regulate fuels under section 211 resides. 
However, EPA's authority to regulate aircraft resides in

[[Page 22446]]

part B of title II, and therefore the definitions of section 216 do not 
apply to aircraft. This means that aircraft are not ``nonroad 
vehicles,'' and aircraft engines are not ``nonroad engines.'' 
Consequently, EPA's authority to regulate fuels under section 211 does 
not extend to fuels used exclusively in aircraft, such as leaded avgas, 
that are not also used in motor vehicles or nonroad vehicles or engines 
(excluding fuel used in vehicles exclusively).
    Instead, fuels used exclusively in aircraft engines are to be 
regulated by the FAA. Title 49 (49 U.S.C. 44714) requires that ``the 
Administrator of the Federal Aviation Administration shall prescribe 
(1) standards for the composition or chemical or physical properties of 
an aircraft fuel or fuel additive to control or eliminate aircraft 
emissions the Administrator of the Environmental Protection Agency 
decides under section 231 of the Clean Air Act (42 U.S.C. 7571) 
endanger the public health or welfare; and (2) regulations providing 
for carrying out and enforcing those standards.''

E. Federal Actions To Reduce Lead Exposure

    The U.S. has made tremendous progress in reducing lead 
concentrations in the outdoor air. Nationwide, average concentrations 
of lead in the air have dropped 91 percent between 1980 and 2008.\33\ 
Much of this dramatic improvement occurred as a result of the permanent 
phase-out of lead in motor vehicle gasoline discussed in this section 
of the ANPR. However, lead continues to be emitted into the air from 
many different types of stationary sources and piston-engine aircraft 
as well as certain high performance engines such as race cars.
---------------------------------------------------------------------------

    \33\ See http://www.epa.gov/airtrends/lead.html.
---------------------------------------------------------------------------

    Federal programs provide for nationwide reductions in emissions of 
lead and other air pollutants through several provisions in the CAA. In 
the early 1970s, EPA issued regulations regarding lead in gasoline in 
order to accomplish two purposes.\34\ First, EPA issued regulations 
designed to ensure the availability of unleaded gasoline for use in 
motor vehicles equipped with emission control systems such as catalytic 
converters. EPA had determined that lead additives would impair to a 
significant degree the performance of emission control systems. Second, 
EPA issued regulations designed to gradually reduce the content of lead 
in leaded gasoline, because EPA found that lead emissions from motor 
vehicles presented a significant risk of harm to the health of urban 
population groups, especially children. Children are at a sensitive 
life stage with regard to the adverse health effects of lead. In 1985, 
EPA, noting the significant reduction in adverse health effects, mainly 
among pre-school age children, that would result from reductions in 
lead content in gasoline, promulgated additional regulations to 
decrease the allowable concentration of lead in gasoline for motor 
vehicles to 0.10 grams per gallon.\35\ In 1990 Congress added section 
211(n) to the CAA which provides that after December 31, 1995, it shall 
be unlawful to sell any gasoline for use in any motor vehicle which 
contains lead or lead additives. In 1996, EPA incorporated the CAA 
statutory ban on gasoline containing lead or lead additives for highway 
use into the Agency's existing regulations on the lead content of 
gasoline.\36\ In this regulation, it was noted that the petroleum 
industry may continue to make and market gasoline produced with lead 
additives for all remaining uses, including use as fuel in aircraft, 
racing cars, and nonroad engines such as farm equipment engines and 
marine engines, to the extent otherwise allowed by law.\37\
---------------------------------------------------------------------------

    \34\ ``Regulation of Fuels and Fuel Additives'' 38 FR 1254 (Dec. 
4, 1973).
    \35\ ``Regulation of Fuels and Fuel Additives; Gasoline Lead 
Content'' 50 FR 9386 (March 7, 1985).
    \36\ ``Prohibition on Gasoline Containing Lead or Lead Additives 
for Highway Use'' 61 FR 3832 (Feb. 2, 1996).
    \37\ ``Prohibition on Gasoline Containing Lead or Lead Additives 
for Highway Use'' 61 FR 3834 (Feb. 2, 1996).
---------------------------------------------------------------------------

    In fact, there have been no regulatory limits placed on the 
production and consumption of leaded avgas, and, as noted in Section 
I.A of this ANPR, emissions of lead from piston-engine aircraft account 
for an increasing fraction of the lead emissions to air (e.g., 
accounting for approximately half the national inventory of lead 
emission in 2005). This is in spite of the decrease in the supply of 
leaded avgas nationally from 374 million gallons (875 tons of lead) in 
1990 to 235 million gallons (550 tons of lead) in 2008.\38\ The 
decrease in fuel consumption is attributed to the decrease in piston-
engine aircraft activity over that time period and not due to a shift 
to unleaded fuel. There are over 200,000 piston-engine aircraft in the 
U.S. that continue to consume leaded avgas and approximately 2,000 new 
piston-engine aircraft requiring leaded avgas are manufactured 
annually. Projected growth for this industry is discussed in Section 
III.B.
---------------------------------------------------------------------------

    \38\ These fuel volume estimates are from the Department of 
Energy Information Administration. http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm.
---------------------------------------------------------------------------

    Significant reductions in emission of lead from stationary sources 
have been achieved between 1985 and 2002, totaling almost 2,000 tons of 
lead.\39\ Regulations promulgated in 1995, 1997 and 1999 controlled 
emissions of lead from primary and secondary lead smelters, 
contributing to these reductions.40 41 42 Currently, metal 
industry emissions of lead comprise 23% of the national inventory (298 
tons). Additional reductions in the emission of lead have been 
accomplished through controls on waste incineration and other 
stationary sources.43 44 45 These standards have been set at 
``maximum achievable control technology'' (MACT) levels, and under CAA 
sections 112 and 129 EPA must revisit these standards in the future to 
determine whether they are sufficiently stringent to provide an ample 
margin of safety to protect public health and prevent an adverse 
environmental effect.
---------------------------------------------------------------------------

    \39\ U.S. Environmental Protection Agency (2008) EPA's Report on 
the Environment EPA/600/R-07/045F. Available at: http://www.epa.gov/roe/.
    \40\ ``National Emission Standards for Hazardous Air Pollutants 
From Secondary Lead Smelting'' 60 FR 32587 (June 23, 1995).
    \41\ ``National Emission Standards for Hazardous Air Pollutants 
From Secondary Lead Smelting'' 62 FR 32209 (June 13, 1997).
    \42\ ``National Emission Standards for Hazardous Air Pollutants 
for Primary Lead Smelting'' 64 FR 30194 (June 4, 1999).
    \43\ ``Standards of Performance for New Stationary Sources and 
Emission Guidelines for Existing Sources: Municipal Waste 
Combustors'' 60 FR 65387 (Dec. 19, 1995).
    \44\ ``Emission Guidelines for Existing Sources and Standards of 
Performance for New Stationary Sources'' 62 FR 45124 (Aug. 25, 
1997).
    \45\ ``Standards of Performance for New Stationary Sources and 
Emission Guidelines for Existing Sources: Large Municipal Waste 
Combustors'' 71 FR 27324-27348 (May 10, 2006).
---------------------------------------------------------------------------

    As lead is a multimedia pollutant, a broad range of Federal 
programs beyond those that focus on air pollution control provide for 
nationwide reductions in environmental releases and human exposures. In 
addition, the U.S. Centers for Disease Control and Prevention (CDC) 
programs provide for the tracking of children's blood lead levels 
nationally and provide guidance on levels at which medical and 
environmental case management activities should be 
implemented.46 47 In

[[Page 22447]]

1991, the Secretary of the U.S. Department of Health and Human Services 
(HHS) characterized lead poisoning as the ``number one environmental 
threat to the health of children in the United States.'' \48\ In 1997, 
President Clinton created, by Executive Order 13045, the President's 
Task Force on Environmental Health Risks and Safety Risks to Children 
in response to increased awareness that children face disproportionate 
risks from environmental health and safety hazards (62 FR 19885).\49\ 
By Executive Orders issued in October 2001 and April 2003, President 
Bush extended the work for the Task Force for an additional three and a 
half years beyond its original charter (66 FR 52013 and 68 FR 19931). 
The Task Force set a Federal goal of eliminating childhood lead 
poisoning by the year 2010, and reducing lead poisoning in children was 
identified as the Task Force's top priority.
---------------------------------------------------------------------------

    \46\ Centers for Disease Control and Prevention (2005) 
Preventing lead poisoning in young children: a statement by the 
Centers for Disease Control and Prevention. Atlanta, GA: U.S. 
Department of Health and Human Services, Public Health Service. 
August.
    \47\ Advisory Committee on Childhood Lead Poisoning Prevention 
(2007) Interpreting and managing blood lead levels <10 [micro]g/dL 
in children and reducing childhood exposures to lead: 
Recommendations of CDC's Advisory Committee on Childhood Lead 
Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR-
8). November 2, 2007.
    \48\ Alliance to End Childhood Lead Poisoning (1991) The First 
Comprehensive National Conference; Final Report. October 6, 7, 8, 
1991.
    \49\ Co-chaired by the Secretary of the HHS and the 
Administrator of the EPA, the Task Force consisted of 
representatives from 16 Federal departments and agencies.
---------------------------------------------------------------------------

    Federal abatement programs provide for the reduction in human 
exposures and environmental releases from in-place materials containing 
lead (e.g., lead-based paint, urban soil and dust, and contaminated 
waste sites). Federal regulations on disposal of lead-based paint waste 
help facilitate the removal of lead-based paint from residences (68 FR 
36487). Further, in 1991, EPA lowered the maximum levels of lead 
permitted in public water systems from 50 parts per billion (ppb) to 15 
ppb measured at the consumer's tap (56 FR 26460).
    Federal programs to reduce exposure to lead in paint, dust, and 
soil are specified under the comprehensive Federal regulatory framework 
developed under the Residential Lead-Based Paint Hazard Reduction Act 
(Title X). Under Title X and Title IV of the Toxic Substances Control 
Act (TSCA), EPA has established regulations and associated programs 
with the goal of reducing exposure to lead via lead-based paint. For 
example, under Title IV of TSCA, EPA established standards identifying 
hazardous levels of lead in residential paint, dust, and soil in 2001. 
On March 31, 2008, the Agency issued a new rule (73 FR 21692) to 
further protect children from lead-based paint hazards resulting from 
renovation and repair work occurring in housing in which they live.
    Programs associated with the Comprehensive Environmental Response, 
Compensation, and Liability Act (CERCLA or Superfund) and Resource 
Conservation Recovery Act (RCRA) also implement abatement programs, 
reducing exposures to lead and other pollutants. For example, EPA 
determines and implements protective levels for lead in soil at 
Superfund sites and RCRA corrective action facilities. Federal 
programs, including those implementing RCRA, provide for management of 
hazardous substances in hazardous and municipal solid waste.\50\ 
Federal regulations concerning batteries in municipal solid waste 
control the collection and recycling or proper disposal of batteries 
containing lead.\51\ Similarly, Federal programs provide for the 
reduction in environmental releases of hazardous substances such as 
lead in the management of wastewater.\52\
---------------------------------------------------------------------------

    \50\ See, e.g., 66 FR 58258.
    \51\ See, e.g., ``Implementation of the Mercury-Containing and 
Rechargeable Battery Management Act'' http://www.epa.gov/epaoswer/hazwaste/recycle/battery.pdf and ``Municipal Solid Waste Generation, 
Recycling, and Disposal in the United States: Facts and Figures for 
2005'' http://www.epa.gov/epaoswer/osw/conserve/resources/msw-2005.pdf.
    \52\ http://www.epa.gov/owm/.
---------------------------------------------------------------------------

    A variety of Federal nonregulatory programs also provide for 
reduced environmental release of lead-containing materials through 
voluntary measures and more general encouragement of pollution 
prevention, promotion of reuse and recycling, reduction of priority and 
toxic chemicals in products and waste, and conservation of energy and 
materials. These include the voluntary partnership between EPA and the 
National Association for Stock Car Auto Racing (NASCAR) which has 
achieved the goal of removing alkyl lead (organic forms of lead) from 
racing fuels used in the Nextel Cup, Busch and Craftsman Truck 
Series.\53\ Other programs include the Resource Conservation 
Challenge,\54\ the National Waste Minimization Program,\55\ ``Plug in 
to eCycling'' (a partnership between EPA and consumer electronics 
manufacturers and retailers),\56\ and activities to reduce the practice 
of backyard trash burning.\57\
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    \53\ U.S. Environmental Protection Agency Persistent, 
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT 
national action plan for alkyl-Pb. Washington, DC. Available online 
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
    \54\ http://www.epa.gov/epawaste/rcc/index.htm.
    \55\ http://www.epa.gov/epawaste/hazard/wastemin/.
    \56\ http://www.epa.gov/epawaste/partnerships/plugin/index.htm.
    \57\ http://www.epa.gov/epawaste/nonhaz/municipal/backyard/index.htm.
---------------------------------------------------------------------------

    In addition to the lead control programs summarized above, EPA's 
research program, with other Federal agencies, identifies, encourages 
and conducts research needed to locate and assess serious risks and to 
develop methods and tools to characterize and help reduce risks. For 
example, EPA's Integrated Exposure Uptake Biokinetic Model for Lead in 
Children (IEUBK model) and the Adult Lead Methodology are widely used 
and accepted as tools that provide guidance in evaluating site specific 
data. More recently, in recognition of the need for a single model that 
predicts lead concentrations in tissue for children and adults, EPA is 
developing the All Ages Lead Model (AALM) to provide researchers and 
risk assessors with a pharmacokinetic model capable of estimating 
blood, tissue, and bone concentrations of lead based on estimates of 
exposure over the lifetime of the individual. EPA research activities 
on substances including lead focus on better characterizing aspects of 
health and environmental effects, exposure, and control or management 
of environmental releases.\58\
---------------------------------------------------------------------------

    \58\ http://www.epa.gov/ord/.
---------------------------------------------------------------------------

II. Health and Welfare Effects of Lead

A. Multimedia and Multi-Pathway Exposure Considerations

    This section briefly summarizes the information presented in the 
2008 NAAQS for Lead,\59\ the 2007 Lead Staff Paper \60\ and the 2006 
Air Quality Criteria Document for Lead (AQCD for Lead).\61\ Lead is an 
unusual pollutant in that the distribution of lead to different 
environmental media (e.g., air, soil, water) is important for 
evaluating public health and welfare effects. Lead emitted to the air 
can result in exposure via multiple pathways (e.g., inhalation, 
ingestion, dermal absorption). Some key multimedia and multi-pathway 
considerations for lead include the following:
---------------------------------------------------------------------------

    \59\ National Ambient Air Quality Standards for Lead 73 FR 
66970-67007 (Nov. 12, 2008) Section II.A.
    \60\ U.S. Environmental Protection Agency Review of the National 
Ambient Air Quality Standards for Lead: Policy Assessment of 
Scientific and Technical Information OAQPS Staff Paper (2007) 
Chapter 2. EPA-452/R-07-013 November.
    \61\ U.S. Environmental Protection Agency Air Quality Criteria 
for Lead (2006) Volume I: Chapters 2 & 3. EPA/600/R-5/144aF. 
October.
---------------------------------------------------------------------------

    (1) Lead is emitted into the air from many sources encompassing a 
wide

[[Page 22448]]

variety of stationary and mobile source types. Lead emitted to the air 
is predominantly in particulate form, with the particles occurring in 
various sizes. Once emitted, the particles can be transported long or 
short distances depending on their size, which influences the amount of 
time spent in the aerosol phase. In general, larger particles tend to 
deposit more quickly, within shorter distances from emissions points 
(e.g., kilometers), while smaller particles will remain in the aerosol 
phase and travel longer distances before depositing (e.g., hundreds to 
thousands of kilometers).\62\ As summarized in the AQCD for Lead, 
airborne concentrations of lead at sites near sources are much higher 
than at sites not known to be directly influenced by sources.
---------------------------------------------------------------------------

    \62\ U.S. Environmental Protection Agency (2004) Air quality 
criteria for particulate matter. Research Triangle Park, NC: Office 
of Research and Development, National Center for Environmental 
Assessment; EPA report no. EPA-600/P-99/0028aF.
---------------------------------------------------------------------------

    (2) Once deposited to surfaces, lead can subsequently be 
resuspended into the ambient air and, because of the persistence of 
lead, emissions of this metal contribute to environmental media 
concentrations for many years into the future as it is cycled within 
and between environmental media such as soil, air and water. Lead that 
is a soil or dust contaminant today may have been airborne yesterday or 
many years ago.\63\
---------------------------------------------------------------------------

    \63\ National Ambient Air Quality Standards for Lead 73 FR 66971 
(Nov. 12, 2008), AQC for Lead, Section 2.5.
---------------------------------------------------------------------------

    (3) Exposure to lead emitted into the ambient air can occur 
directly by inhalation, or indirectly by ingestion of lead-contaminated 
food, water or other materials including dust and soil. This occurs due 
to the environmental cycling of this persistent metal which, once 
emitted into the ambient air is distributed to other environmental 
media and can contribute to human exposures via indoor and outdoor 
dusts, outdoor soil, food and drinking water, as well as inhalation of 
air. Atmospheric deposition is estimated to comprise a significant 
proportion of lead in food (AQCD for Lead, p. 3-48). For example, 
livestock may be exposed to lead in vegetation (e.g., grasses and 
silage) and in surface soils via incidental ingestion of soil while 
grazing (USEPA 1986, Section 7.2.2.2.2).\64\ And dietary intake may be 
a predominant source of lead exposure among adults, greater than 
consumption of water and beverages or inhalation (73 FR 66971). These 
exposure pathways are described more fully in Section 8.2.2 of the AQCD 
for Lead.
---------------------------------------------------------------------------

    \64\ U.S. Environmental Protection Agency (1986) Air quality 
criteria for lead. Research Triangle Park, NC: Office of Health and 
Environmental Assessment, Environmental Criteria and Assessment 
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from: 
NTIS, Springfield, VA; PB87-142378.
---------------------------------------------------------------------------

    (4) Air-related exposure pathways are affected by changes to air 
quality, including changes in concentrations of lead in air and changes 
in atmospheric deposition of lead. Further, because of its persistence 
in the environment, lead deposited from the air may contribute to human 
and ecological exposures for years into the future as described above.
    Additionally, human exposures to lead include pathways that are not 
related to ambient air concentrations. The pathways of human exposure 
to lead that are not air-related include ingestion of indoor lead 
paint,\65\ lead in diet as a result of inadvertent additions during 
food processing, and lead in drinking water attributable to lead in 
distribution systems, as well as other generally less prevalent 
pathways, as described in the AQCD for Lead (pp. 3-50 to 3-51).
---------------------------------------------------------------------------

    \65\ Weathering of outdoor lead paint may also contribute to 
soil lead levels adjacent to the house.
---------------------------------------------------------------------------

B. Health Effects Information

    In 2008, EPA decreased the level of the primary (health-based) 
NAAQS for Lead from 1.5 [mu]g/m\3\ to 0.15 [mu]g/m\3\ in order to 
provide increased protection for children and other at-risk populations 
against an array of adverse health effects, most notably neurological 
effects in children, including neurocognitive and neurobehavioral 
effects.\66\ This section summarizes information provided in the 
numerous recent documents summarizing health and welfare effects from 
exposure to lead, including the AQCD for Lead, CDC documents, the EPA 
Staff Paper \67\ and the proposed and final NAAQS for Lead. First, the 
use of blood lead as a measure of exposure to lead is described 
followed by a brief summary of the broad array of lead-induced health 
effects. Particular focus is given here to the effects of lead on the 
developing nervous system in children since this is among the most 
sensitive endpoints identified for this toxic metal. The section ends 
with a description of at-risk populations and life stages.
---------------------------------------------------------------------------

    \66\ National Ambient Air Quality Standards for Lead 73 FR 66965 
(Nov. 12, 2008).
    \67\ U.S. Environmental Protection Agency (2007) Review of the 
National Ambient Air Quality Standards for Lead: Policy Assessment 
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research 
Triangle Park.
---------------------------------------------------------------------------

1. Blood Lead
    Lead enters the body most commonly via the respiratory system and/
or gastrointestinal tract, from which it is quickly absorbed into the 
blood stream and distributed throughout the body.\68\ Less commonly, 
lead, particularly organic forms of lead such as alkyl lead, can be 
absorbed through the skin (AQCD for Lead, page 4-12). Blood lead levels 
are extensively used as an index or biomarker of exposure by national 
and international health agencies, as well as in epidemiological (AQCD 
for Lead, Sections 4.3.1.3 and 8.3.2) and toxicological studies of lead 
health effects and dose-response relationships (AQCD for Lead, Chapter 
5). The U.S. CDC, and its predecessor agencies, has for many years used 
blood lead level as a metric for identifying children at risk of 
adverse health effects and for specifying particular public health 
recommendations.\69\ Most recently, in 2005, with consideration of a 
review of the evidence by their advisory committee, CDC revised their 
statement on Preventing Lead Poisoning in Young Children.\70\ CDC 
specifically recognized the evidence of adverse health effects in 
children with blood lead levels below 10 [mu]g/dL,\71\ the data 
demonstrating that no ``safe'' threshold for blood lead had been 
identified, and emphasized the importance of preventative measures.\72\
---------------------------------------------------------------------------

    \68\ Additionally, lead freely crosses the placenta resulting in 
continued fetal exposure throughout pregnancy, with that exposure 
increasing during the latter half of pregnancy (AQC for Lead, 
Section 6.6.2).
    \69\ Centers for Disease Control (1991) Preventing lead 
poisoning in young children: a statement by the Centers for Disease 
Control. Atlanta, GA: U.S. Department of Health and Human Services, 
Public Health Service; October 1. Available online at: http://wonder.cdc.gov/wonder/prevguid/p0000029/p0000029.asp.
    \70\ Centers for Disease Control and Prevention (2005) 
Preventing lead poisoning in young children: a statement by the 
Centers for Disease Control and Prevention. Atlanta, GA: U.S. 
Department of Health and Human Services, Public Health Service. 
August.
    \71\ As described by the Advisory Committee on Childhood Lead 
Poisoning Prevention, ``In 1991, CDC defined the blood lead level 
(BLL) that should prompt public health actions as 10 [mu]g/dL. 
Concurrently, CDC also recognized that a BLL of 10 [mu]g/dL did not 
define a threshold for the harmful effects of lead. Research 
conducted since 1991 has strengthened the evidence that children's 
physical and mental development can be affected at BLLS <10 [mu]g/
dL'' (ACCLPP, 2007).
    \72\ Advisory Committee on Childhood Lead Poisoning Prevention 
(2007) Interpreting and managing blood lead levels <10 [mu]g/dL in 
children and reducing childhood exposures to lead: Recommendations 
of CDC's Advisory Committee on Childhood Lead Poisoning Prevention. 
Morbidity and Mortality Weekly Report. 56(RR-8). November 2, 2007.
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    Since 1976, the CDC has been monitoring blood lead levels in 
multiple age groups nationally through the National Health and 
Nutrition Examination Survey (NHANES).\73\ The

[[Page 22449]]

NHANES information has documented the dramatic decline in mean blood 
lead levels in the U.S. population that has occurred since the 1970s 
and that coincides with regulations regarding leaded motor vehicle 
fuels, leaded paint, and lead-containing plumbing materials that have 
reduced lead exposure among the general population (AQCD for Lead, 
Sections 4.3.1.3 and 8.3.3).
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    \73\ This information documents a variation in mean blood lead 
levels across the various age groups monitored. For example, mean 
blood lead levels in 2001-2002 for ages 1-5, 6-11, 12-19 and greater 
than or equal to 20 years of age, are 1.70, 1.25, 0.94, and 1.56 
[mu]g/dL, respectively (AQC for Lead, p. 4-22).
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    While blood lead levels in the U.S. general population, including 
geometric mean levels in children aged 1-5 have declined significantly, 
levels have been found to vary among children of different 
socioeconomic status (SES) and other demographic characteristics (AQCD 
for Lead, p. 4-21), as well as by age.\74\ Racial/ethnic and income 
disparities in blood lead levels in children persist. For example, 
blood lead levels for lower income and African American children are 
higher than those for the general population.
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    \74\ Axelrad, D., U.S. EPA (November 4, 2009) E-mail message to 
Marion Hoyer, U.S. EPA. Available in docket number EPA-HQ-OAR-2007-
0294.
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    The spectrum of health effects discussed in the following section 
is relevant for all forms of lead that enter the blood stream. Once in 
the blood stream, lead bioaccumulates in the body, with the bone 
serving as a large, long-term storage compartment. Soft tissues (e.g., 
kidney, liver, brain, etc.) serve as smaller compartments, in which 
lead may be more mobile (AQCD for Lead, Sections 4.3.1.4 and 8.3.1). 
During childhood development, bone represents approximately 70% of a 
child's body burden of lead, and this accumulation continues through 
adulthood, when more than 90% of the total lead body burden is stored 
in the bone (AQCD for Lead, Section 4.2.2). Lead in bone can be 
mobilized during critical periods including pregnancy and lactation 
(AQCD for Lead, Section 5.8.6).
2. Health Effects
    Lead, as with mercury and arsenic, has no known biological 
function.\75\ Lead has been demonstrated to exert ``a broad array of 
deleterious effects on multiple organ systems via widely diverse 
mechanisms of action'' (AQCD for Lead, p. 8-24 and Section 8.4.1). This 
array of health effects includes effects on heme biosynthesis and 
related functions; neurological development and function; reproduction 
and physical development; kidney function; cardiovascular function; and 
immune function. The weight of evidence varies across this array of 
effects and is comprehensively described in the AQCD for Lead. There is 
also some evidence of lead carcinogenicity, primarily from animal 
studies, together with limited human evidence of suggestive 
associations (AQCD for Lead, Sections 5.6.2, 6.7, and 8.4.10). The U.S. 
EPA has listed lead under current EPA guidelines as a probable human 
carcinogen based on the available animal data (AQCD for Lead, p. 6-
195).\76\ Inorganic lead has been classified as a probable human 
carcinogen by the International Agency for Research on Cancer 
(inorganic lead compounds), based mainly on sufficient animal 
evidence,\77\ and classified as reasonably anticipated to be a human 
carcinogen by the U.S. National Toxicology Program (lead and lead 
compounds) (AQCD for Lead, Section 6.7.2).78 79
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    \75\ U.S. Environmental Protection Agency (2007) Framework for 
Metals Risk Assessment. Office of the Science Advisor. EPA 120/R-07/
001.
    \76\ U.S. Environmental Protection Agency, Integrated Risk 
Information System (IRIS) (1993) IRIS Summary for Lead and compounds 
(CASRN 7439-92-1), Available online at: http://www.epa.gov/ncea/iris/subst/0277.htm.
    \77\ International Agency for Research on Cancer (IARC) (2006) 
Inorganic and organic lead compounds. Lyon, France: International 
Agency for Research on Cancer. IARC monographs on the evaluation of 
the carcinogenic risk of chemicals to humans: volume 87. Available 
online at: http://monographs.iarc.fr/ENG/Monographs/vol87/index.php.
    \78\ National Toxicology Program (2003) Report on carcinogens 
background document for lead and lead compounds. Research Triangle 
Park, NC: U.S. Department of Health and Human Services. Available 
online at: http://ntp.niehs.nih.gov/ntp/newhomeroc/roc11/Lead-Public.pdf.
    \79\ National Toxicology Program. (2004) Lead (CAS no. 7439-92-
1) and lead compounds. In: Report on carcinogens, eleventh edition. 
Research Triangle Park, NC: U.S. Department of Health and Human 
Services. Available online at: http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s101lead.pdf.
---------------------------------------------------------------------------

    As described in the AQCD for Lead, the key effects associated with 
individual blood lead levels in children and adults in the range of 10 
[mu]g/dL and lower include neurological, hematological and immune \80\ 
effects for children, and hematological, cardiovascular and renal 
effects for adults (AQCD for Lead, Tables 8-5 and 8-6, pp. 8-60 to 8-
62). As evident from the discussions in Chapters 5, 6 and 8 of the AQCD 
for Lead, ``neurotoxic effects in children and cardiovascular effects 
in adults are among those best substantiated as occurring at blood lead 
concentrations as low as 5 to 10 [mu]g/dL (or possibly lower); and 
these categories are currently clearly of greatest public health 
concern'' (AQCD for Lead, p. 8-60).81 82 The AQCD for Lead 
states, ``There is no level of lead exposure that can yet be 
identified, with confidence, as clearly not being associated with some 
risk of deleterious health effects'' (AQCD for Lead, p. 8-63).
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    \80\ At mean blood lead levels, in children, on the order of 10 
[mu]g/dL, and somewhat lower, associations have been found with 
effects to the immune system, including altered macrophage 
activation, increased IgE levels and associated increased risk for 
autoimmunity and asthma (AQC for Lead, Sections 5.9, 6.8, and 
8.4.6).
    \81\ With regard to blood lead levels in individual children 
associated with particular neurological effects, the AQC for Lead 
states ``Collectively, the prospective cohort and cross-sectional 
studies offer evidence that exposure to lead affects the 
intellectual attainment of preschool and school age children at 
blood lead levels <10 [mu]g/dL (most clearly in the 5 to 10 [mu]g/dL 
range, but, less definitively, possibly lower).'' (p. 6-269)
    \82\ Epidemiological studies have consistently demonstrated 
associations between lead exposure and enhanced risk of deleterious 
cardiovascular outcomes, including increased blood pressure and 
incidence of hypertension. A meta-analysis of numerous studies 
estimates that a doubling of blood-lead level (e.g., from 5 to 10 
[mu]g/dL) is associated with ~1.0 mm Hg increase in systolic blood 
pressure and ~0.6 mm Hg increase in diastolic pressure (AQC for 
Lead, p. E-10).
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    While adults are susceptible to lead effects at lower blood lead 
levels than previously understood (e.g., AQCD for Lead, p. 8-25), among 
the wide variety of health endpoints associated with lead exposures, 
there is general consensus that the developing nervous system in 
children is among the, if not the, most sensitive. Blood lead levels in 
U.S. children have decreased notably since the late 1970s. Studies 
evaluating current blood lead levels in children have reported 
associations with neurodevelopment effects (AQCD for Lead, Chapter 6). 
Functional manifestations of lead neurotoxicity during childhood 
include sensory, motor, cognitive and behavioral impacts. Numerous 
epidemiological studies have reported neurocognitive, neurobehavioral, 
sensory, and motor function effects in children with blood lead levels 
below 10 [mu]g/dL (AQCD Lead, Sections 6.2 and 8.4).
    Cognitive effects associated with lead exposures that have been 
observed in epidemiological studies have included decrements in 
intelligence test results, such as the widely used IQ score, and in 
academic achievement as assessed by various standardized tests as well 
as by class ranking and graduation rates (AQCD for Lead, Section 6.2.16 
and pp 8-29 to 8-30). As noted in the AQCD for Lead with regard to the 
latter, ``Associations between lead exposure and academic achievement 
observed in the above-noted studies were significant even after 
adjusting for IQ, suggesting that lead-sensitive neuropsychological 
processing and learning factors not

[[Page 22450]]

reflected by global intelligence indices might contribute to reduced 
performance on academic tasks'' (AQCD for Lead, pp 8-29 to 8-30).
    With regard to potential implications of lead effects on IQ, the 
AQCD for Lead recognizes the ``critical'' distinction between 
population and individual risk, identifying issues regarding declines 
in IQ for an individual and for the population. The AQCD for Lead 
further states that a ``point estimate indicating a modest mean change 
on a health index at the individual level can have substantial 
implications at the population level'' (AQCD for Lead, p. 8-77).\83\ A 
downward shift in the mean IQ value is associated with both substantial 
decreases in percentages achieving very high scores and substantial 
increases in the percentage of individuals achieving very low scores 
(AQCD for Lead, p. 8-81).\84\ For an individual functioning in the low 
IQ range due to the influence of developmental risk factors other than 
lead, a lead-associated IQ decline of several points might be 
sufficient to drop that individual into the range associated with 
increased risk of educational, vocational, and social failure (AQCD for 
Lead, p. 8-77).
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    \83\ As an example, the AQC for Lead states ``although an 
increase of a few mmHg in blood pressure might not be of concern for 
an individual's well-being, the same increase in the population mean 
might be associated with substantial increases in the percentages of 
individuals with values that are sufficiently extreme that they 
exceed the criteria used to diagnose hypertension'' (AQC for Lead, 
p. 8-77).
    \84\ For example, for a population mean IQ of 100 (and standard 
deviation of 15), 2.3% of the population would score above 130, but 
a shift of the population to a mean of 95 results in only 0.99% of 
the population scoring above 130 (AQC for Lead, pp. 8-81 to 8-82).
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    Other cognitive effects observed in studies of children have 
included decrements in attention, executive functions, language, 
memory, learning and visuospatial processing (AQCD for Lead, Sections 
5.3.5, 6.2.5 and 8.4.2.1), with attention and executive function 
effects associated with lead exposures indexed by blood lead levels 
below 10 [mu]g/dL (AQCD for Lead, Section 6.2.5 and pp. 8-30 to 8-31). 
The evidence for the role of lead in this suite of effects includes 
experimental animal findings (discussed in the AQCD for Lead, Section 
8.4.2.1; p. 8-31), which provide strong biological plausibility of lead 
effects on learning ability, memory and attention (AQCD for Lead, 
Section 5.3.5), as well as associated mechanistic findings.
    The persistence of such lead-induced effects is described in the 
AQCD for Lead (e.g., AQCD for Lead Sections 5.3.5, 6.2.11, and 8.5.2). 
The persistence or irreversibility of such effects can be the result of 
damage occurring without adequate repair offsets or of the persistence 
of lead in the body (AQCD for Lead, Section 8.5.2). It is additionally 
important to note that there may be long-term consequences of such 
deficits over a lifetime. Poor academic skills and achievement can have 
``enduring and important effects on objective parameters of success in 
real life,'' as well as increased risk of antisocial and delinquent 
behavior (AQCD for Lead, Section 6.2.16).
    The current evidence reviewed in the AQCD for Lead with regard to 
the quantitative relationship between neurocognitive decrement, such as 
IQ, and blood lead levels indicates that the slope for lead effects on 
IQ is nonlinear and is steeper at lower blood lead levels, such that 
each [mu]g/dL increase in blood lead may have a greater effect on IQ at 
lower blood lead levels (e.g., below 10 [mu]g/dL) than at higher levels 
(AQCD for Lead, Section 6.2.13; pp. 8-63 to 8-64; Figure 8-7). As noted 
in the AQCD for Lead, a number of examples of non- or supralinear dose-
response relationships exist in toxicology (AQCD for Lead, pp. 6-76 and 
8-38 to 8-39). With regard to the effects of lead on neurodevelopmental 
outcomes such as IQ, the AQCD for Lead suggests that initial 
neurodevelopmental effects at lower lead levels may be disrupting very 
different biological mechanisms (e.g., early developmental processes in 
the central nervous system) than more severe effects of high exposures 
that result in symptomatic lead poisoning and frank mental retardation 
(AQCD for Lead, p. 6-76). The AQCD for Lead describes this issue in 
detail with regard to lead (summarized in AQCD for Lead at p. 8-39). 
Various findings within the toxicological evidence, presented in the 
AQCD for Lead, provide biologic plausibility for a steeper IQ loss at 
low blood lead levels, with a potential explanation being that the 
predominant mechanism at very low blood lead levels is rapidly 
saturated and that a different, less-rapidly-saturated process becomes 
predominant at blood lead levels greater than 10 [mu]g/dL.
3. At-Risk Populations and Life Stages
    Individuals potentially at risk from exposure to environmental 
pollutants include those with increased susceptibility and 
vulnerability. The terms ``susceptibility'' and ``vulnerability'' have 
been used to characterize those with a greater likelihood of an adverse 
outcome given a specific exposure in comparison with the general 
population. This increased likelihood of response to a pollutant can 
result from a multitude of factors, including genetic or developmental 
factors, life stages (i.e., childhood or old age), gender differences, 
or preexisting disease states. In addition, new attention has been paid 
to the concept of some population groups having increased responses to 
pollution-related effects due to factors including socioeconomic status 
(SES) (e.g., reduced access to health care, poor nutritional status) or 
particularly elevated exposure levels.
    EPA uses the term ``life stage'' to refer to a distinguishable time 
frame in an individual's life characterized by unique and relatively 
stable behavioral and/or physiological characteristics that are 
associated with development and growth. To recognize the rapid changes 
that occur during childhood related to physiology, metabolism, anatomy 
and behavior that can impact exposure and risk to environmental 
hazards, EPA now views childhood as a sequence of life stages, from 
conception through fetal development, infancy, and adolescence. EPA 
published several exposure and risk assessment guidance documents 
beginning in 2005,85 86 87 in which we emphasized the 
importance of considering the potential for increased sensitivity of 
different life stages or age groups in addition to that of groups that 
form a fixed portion of the population based on characteristics such as 
pre-existing disease, gender, socioeconomic status, geographical 
location, culture/ethnicity, or genetic make-up.
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    \85\ U.S. EPA (2005) Guidance on Selecting Age Groups for 
Monitoring and Assessing Childhood Exposure to Environmental 
Contaminants. EPA/630/P-03/003F.
    \86\ U.S. EPA (2006) A Framework for Assessing Health Risks of 
Environmental Exposures to Children. EPA/600/R-05/093A.
    \87\ U.S. EPA (2008) Child-Specific Exposure Factors Handbook. 
EPA/600/R-06/096F.
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    Physiological, behavioral and demographic factors contribute to 
increased risk of lead-related health effects. Children are at 
increased risk of lead-related health effects due to various factors 
that enhance their exposures (e.g., via the hand-to-mouth activity that 
is prevalent in very young children, AQCD for Lead, Section 4.4.3) and 
susceptibility. While children are considered to be at a period of 
maximum exposure around 18-27 months, the current evidence has found 
even stronger associations between blood lead levels at school age and 
IQ at school age. The evidence ``supports the idea that lead exposure 
continues to be toxic to children as they reach school age, and [does] 
not lend support to the interpretation that all the damage is done by 
the time the child reaches 2 to

[[Page 22451]]

3 years of age'' (AQCD for Lead, Section 6.2.12). Physiological factors 
that can affect risk of lead-related effects in children include 
genetic polymorphisms and nutritional status. Children with particular 
genetic polymorphisms (e.g., presence of the [delta]-aminolevulinic 
acid dehydratase-2 [ALAD-2] allele) have increased sensitivity to lead 
toxicity, which may be due to increased susceptibility to the same 
internal dose and/or to increased internal dose associated with the 
same exposure (AQCD for Lead, p. 8-71, Sections 6.3.5, 6.4.7.3 and 
6.3.6). Some children may have blood lead levels higher than those 
otherwise associated with a given lead exposure (AQCD for Lead, Section 
8.5.3) as a result of nutritional status (e.g., iron deficiency, 
calcium intake), as well as genetic and other factors (AQCD for Lead, 
Chapter 4 and Sections 3.4, 5.3.7 and 8.5.3).
    Demographic factors that can affect risk of lead-related effects in 
children include residential location, poverty, and race. As noted in 
previous EPA actions on lead, situations of elevated exposure, such as 
residing near sources of ambient lead, as well as socioeconomic 
factors, such as reduced access to health care or low socioeconomic 
status can also contribute to increased blood lead levels and increased 
risk of associated health effects from air-related lead.\88\ 
Additionally, as described in the NAAQS for Lead, children in poverty 
and black, non-Hispanic children have notably higher blood lead levels 
than do economically well-off children and white children, in 
general.\89\
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    \88\ U.S. Environmental Protection Agency (2007) Review of the 
National Ambient Air Quality Standards for Lead: Policy Assessment 
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research 
Triangle Park.
    \89\ See 73 FR 66973 (November 12, 2008).
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C. Welfare Effects

    Lead is persistent in the environment and accumulates in soils, 
aquatic systems (including sediments), and some biological tissues of 
plants, animals and other organisms, thereby providing long-term, 
multi-pathway exposures to organisms and ecosystems. In 2008, EPA 
established a secondary lead standard of 0.15 ug/m\3\. This standard is 
intended to protect the public welfare from known or anticipated 
adverse effects associated with the presence of lead in the ambient 
air. This section provides a summary of information regarding welfare 
effects of lead, focusing on terrestrial and aquatic ecosystems. This 
information is largely drawn from the 2006 AQCD for Lead, Chapter 6 of 
the Office of Air Quality Planning and Standards Staff Paper on Lead 
(SP) \90\ and the Lead NAAQS.
---------------------------------------------------------------------------

    \90\ U.S. Environmental Protection Agency (2007) Review of the 
National Ambient Air Quality Standards for Lead: Policy Assessment 
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research 
Triangle Park.
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1. Terrestrial Ecosystems
    Lead is removed from the atmosphere and deposited on soil and other 
surfaces via wet or dry deposition. In soils, most lead is retained via 
the formation of stable solid phase compounds, precipitates, or 
complexes with organic matter. Thus, terrestrial ecosystems remain 
primarily sinks for lead but amounts retained in various soil layers 
vary based on forest type, climate, and litter cycling (AQCD for Lead, 
Section 7.1). Once in the soil, the migration and distribution of lead 
is controlled by a multitude of factors including pH, precipitation, 
litter composition and other factors, which in turn, govern the rate at 
which lead is bound to organic materials in the soil (AQCD for Lead, 
Section 2.3.5, and Section AX 7.1.4.1).
    Lead exists in the environment in different forms which vary widely 
in their ability to cause adverse effects on ecosystems and organisms. 
Many forms of lead in the ambient air are quite insoluble and thus not 
easily leached to underground water once deposited to surfaces. 
However, leaching may occur under acidic conditions, where lead 
concentrations are extremely high, or in the presence of substances 
(e.g., soluble organic matter, high concentrations of chlorides or 
sulfates) that form relatively soluble complexes with lead (AQCD for 
Lead, Section 2.3.5).
    Plants take up lead via their foliage and through their root 
systems. The rate of plant uptake from soil varies by plant species, 
soil conditions, and lead species. Most lead in plants is stored in 
roots, and very little is stored in fruits. Metals that are applied to 
soil as salts (usually as sulfate, chloride, or nitrate salt) are 
accumulated more readily than the same quantity of metal added via 
sewage sludge, flue dust, or fly ash (AQCD for Lead, Section 2.3.7).
    Surface deposition of lead onto plants may represent a significant 
contribution to the total lead in and on the plant, as has been 
observed for plants near smelters and along roadsides (AQCD for Lead, 
page E-19). Atmospheric deposition of lead also contributes to lead in 
vegetation as a result of contact with above-ground portions of the 
plant (AQCD for Lead, pp. 7-9 and AXZ7-39; USEPA, 1986, Sections 6.5.3 
and 7.2.2.2.1). Wildlife may subsequently be exposed to lead in 
vegetation (e.g., grasses and silage) and in surface soils via 
incidental ingestion of soil while grazing (USEPA 1986, Section 
7.2.2.2.2).\91\
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    \91\ U.S. Environmental Protection Agency (1986) Air quality 
Criteria for Lead. Research Triangle Park, NC: Office of Health and 
Environmental Assessment, Environmental Criteria and Assessment 
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from: 
NTIS, Springfield, VA; PB87-142378.
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    By far, the majority of air-related lead found in natural 
terrestrial ecosystems was deposited in the past during the use of lead 
additives in motor vehicle gasoline. Many sites receiving lead 
predominantly through long-range transport of gasoline-derived small 
particles have accumulated large amounts of lead in soils (AQCD for 
Lead, p. AX7-98). There is little evidence that terrestrial sites 
exposed as a result of this long range transport of lead have 
experienced significant effects on ecosystem structure or function 
(AQCD for Lead, Section AX7.1.4.2 and p. AX7-98). Strong complexation 
of lead by organic matter in soil may explain why few ecological 
effects have been observed (AQCD for Lead, p. AX7-98). Studies have 
shown decreasing levels of lead in vegetation, which appears to 
correlate with decreases in atmospheric deposition of lead resulting 
from the removal of lead additives to motor vehicle gasoline (AQCD for 
Lead, Section AX 7.1.4.2).
    The deposition of gasoline-derived lead into forest soils has 
produced a legacy of slow moving lead that remains bound to organic 
materials despite dramatic reductions in the use of leaded additives to 
motor vehicle fuels. Current levels of lead in soil vary widely 
depending on the source of lead but in all ecosystems lead 
concentrations exceed natural background levels. For areas influenced 
by point sources of air lead, concentrations of lead in soil may exceed 
by many orders of magnitude the concentrations which are considered 
harmful to laboratory organisms. Adverse effects in terrestrial 
organisms associated with lead include neurological, physiological and 
behavioral effects which may influence ecosystem structure and 
functioning (73 FR 67008).
2. Aquatic Ecosystems
    Atmospheric lead enters aquatic ecosystems primarily through 
deposition (wet and dry) and the erosion and runoff of soils containing 
lead. While overall deposition rates of atmospheric lead have decreased 
dramatically since the removal of lead additives from motor vehicle 
gasoline,

[[Page 22452]]

lead continues to accumulate and may be re-exposed in sediments and 
water bodies throughout the United States (AQCD for Lead, Section 
2.3.6).
    Several physical and chemical factors govern the fate and 
bioavailability of lead in aquatic systems. A significant portion of 
lead remains bound to suspended particulate matter in the water column 
and eventually settles into the substrate. Species, pH, salinity, 
temperature, turbulence and other factors govern the bioavailability of 
lead in surface waters (AQCD for Lead, Section 7.2.2). Lead can 
bioaccumulate in the tissues of aquatic organisms through ingestion of 
food and water, and adsorption from water, and can subsequently lead to 
adverse effects if tissue levels are sufficiently high.\92\ The 
accumulation of lead is influenced by pH and decreasing pH favors 
bioavailability and bioaccumulation. Organisms that bioaccumulate lead 
with little excretion must partition the metal such that it has limited 
bioavailability, otherwise toxicity will occur if a sufficiently high 
concentration is reached.\93\ The general symptoms of lead toxicity in 
fish include production of excess mucus, lordosis, anemia, darkening of 
the dorsal tail region, degeneration of the caudal fin, destruction of 
spinal neurons, aminolevulinic acid dehydratase (ALAD) inhibition, 
growth inhibition, renal pathology, reproductive effects, growth 
inhibition, and mortality.\94\ Toxicity in fish has been closely 
correlated with duration of lead exposure and uptake.\95\
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    \92\ AQC for Lead I. 7-24: (Vink, 2002; Rainbow, 1996).
    \93\ AQC for Lead AX7.2.3.1.
    \94\ AQC for Lead page 232, Annex 7.
    \95\ AQC for Lead page 232, Annex 7.
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    Lead exists in the aquatic environment in various forms and under 
various chemical and physical parameters which determine the ability of 
lead to cause adverse effects either from dissolved lead in the water 
column or lead in sediment. Current levels of lead in water and 
sediment vary widely depending on the source of lead. Conditions exist 
in which adverse effects to organisms and thereby ecosystems may be 
anticipated given experimental results. It is unlikely that dissolved 
lead in surface water constitutes a threat to ecosystems that are not 
directly influenced by point sources. For lead in sediment, the 
evidence regarding the effects is less clear. It is likely that some 
areas with long-term historical deposition of lead to sediment from a 
variety of sources as well as areas influenced by point sources have 
the potential for adverse effects to aquatic communities. The long 
residence time of lead in sediment and its ability to be resuspended by 
turbulence make lead likely to be a factor for consideration regarding 
potential risk to aquatic systems for the foreseeable future (73 FR 
67008).

III. Lead Emissions From Piston-Engine Aircraft

    Currently, lead emitted by piston-engine aircraft operating on 
leaded avgas is the largest source of lead to the air, contributing 
about 50% of the National Emission Inventory in 2005. This section 
describes the draft 2008 avgas lead inventory which is currently 
undergoing review by State, local and Tribal air agencies. We describe 
and request comment on input data used to derive airport-specific lead 
inventories. This section ends with a summary of data forecasting the 
potential growth of the industry using leaded avgas.

A. Inventory of Lead From Piston-Engine Powered Aircraft

    Every three years, the EPA prepares a National Emissions Inventory 
(NEI) of air emissions of criteria pollutants and hazardous air 
pollutants with input from numerous State, local, and Tribal air 
agencies and from industry.\96\ For the purposes of this ANPR, EPA is 
describing piston-engine aircraft lead information provided in the 
draft 2008 NEI as well as information from the final 2005 NEI. We have 
chosen to describe the draft 2008 NEI for the following reasons: (1) 
This is the first version of the NEI that will include airport-specific 
lead inventories that use our most recently developed methods for 
estimating lead (described below); (2) this inventory is the first NEI 
to include approximately 20,000 airport facilities in the U.S.; and (3) 
to increase awareness of the opportunity for State, local, and Tribal 
governments and industry to review this draft NEI and provide 
information that could improve airport lead inventories. Comments and 
data can be supplied to EPA for the 2008 NEI until mid-2010. While we 
are describing the draft 2008 NEI for piston-engine aircraft emissions 
of lead, we do not have draft inventory estimates for 2008 for all 
sources of lead. The 2008 NEI will be final in 2010.
---------------------------------------------------------------------------

    \96\ http://www.epa.gov/air/data/neidb.html.
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1. National Emissions of Lead From Piston-Engine Aircraft
    To calculate the national avgas lead inventory, the volume of 
leaded avgas produced in a given year is multiplied by the 
concentration of lead in the avgas and by the fraction of lead emitted 
from a combustion system operating on leaded fuel (to account for the 
lead that is retained in the engine, engine oil and/or exhaust system). 
For example, the volume of avgas produced in the U.S. in 2008 according 
to DOE was 235,326,000 gallons.\97\ The concentration of lead in avgas 
([Pb] in the equation below) can be one of four levels (ranging from 
0.14 to 1.12 grams of lead per liter or 0.53 to 4.24 grams of lead per 
gallon) as specified by the American Society for Testing and Materials 
(ASTM). By far the most common avgas supplied is ``100 Low Lead'' or 
100LL which has a maximum lead concentration specified by ASTM of 0.56 
grams per liter or 2.12 grams per gallon.98 99 A fraction of 
lead is retained in the engine, engine oil and/or exhaust system which 
we currently estimate at 5%.\100\
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    \97\ DOE Energy Information Administration. Fuel production 
volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm accessed November 2006.
    \98\ ChevronTexaco (2006) Aviation Fuels Technical Review. FTR-
3. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
    \99\ ASTM International (2007) Standard Specification for 
Aviation Gasolines D910-06.
    \100\ U.S. Environmental Protection Agency (2008) Lead Emissions 
from the Use of Leaded Aviation Gasoline in the United States, 
Technical Support Document. EPA420-R-08-020. Available online at: 
http://www.epa.gov/otaq/aviation.htm.
---------------------------------------------------------------------------

    For 2008, using DOE fuel volume estimates, the national estimate of 
lead emissions from the consumption of avgas is 522 tons as calculated 
according to the following equation:
[GRAPHIC] [TIFF OMITTED] TP28AP10.015


[[Page 22453]]


    As described in the Overview section of this ANPR, DOT's FAA also 
provides estimates of annual avgas fuel consumption. For 2008, DOT 
estimates 351,000,000 gallons of avgas were consumed. Consumption of 
this volume of avgas equates to a national lead emissions estimate for 
this source of 779 short tons. DOT fuel volume data are derived from 
FAA estimates of piston-engine activity annually.\101\ We are working 
to identify the source(s) of the information used to derive DOE fuel 
volume estimates. In the draft 2008 NEI, we are using DOT fuel volume 
estimates.
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    \101\ U.S. Department of Transportation Federal Aviation 
Administration Aviation Policy and Plans. FAA Aerospace Forecast 
Fiscal Years 2009-2025. p.81. Available at: http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009-2025/media/2009%20Forecast%20Doc.pdf. This document provides historical data 
for 2000-2008 as well as forecast data.
---------------------------------------------------------------------------

    We currently cannot estimate the fraction of total lead emissions 
these estimates comprise since the inventories for all other sources of 
lead to air are not yet in the draft 2008 NEI. In 2005, lead from avgas 
comprised about 50% of the national lead inventory for emissions to 
air. As point source emissions of lead have decreased, lead emissions 
from piston-engine aircraft have become the largest single source of 
lead to air (Figure 2). These lead emissions estimates do not include 
evaporative losses of lead and minimal military aircraft data. Few 
military aircraft are piston-engine powered and consume leaded 
avgas.\102\ Military aircraft data are supplied by States, and data 
provided to EPA during the 2008 NEI review will be included in the 
final 2008 inventory.
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    \102\ ChevronTexaco (2006) Aviation Fuels Technical Review p. 
44. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
[GRAPHIC] [TIFF OMITTED] TP28AP10.016

2. Airport-Specific Emissions of Lead From Piston-Engine Aircraft
    Aircraft gaseous and particulate matter (PM) emissions are 
calculated through the FAA's Emissions and Dispersion Modeling System 
(EDMS).\103\ This modeling system was designed to develop emission 
inventories for the purpose of assessing potential air quality impacts 
of airport operations and proposed airport development projects. Lead 
emissions from piston-engine aircraft are not included in EDMS. To 
estimate airport-specific lead inventories we use engine data and other 
attributes of general aviation (GA) and air taxi (AT) that are used in 
EDMS for GA and AT and we use methods similar to those in EDMS that are 
described in an EPA Technical Support Document (TSD) and briefly

[[Page 22454]]

summarized here.\104\ The data required to estimate airport-specific 
lead inventories includes the landing and take-off (LTO) activity of 
piston-engine aircraft at a facility; fuel consumption rates by these 
aircraft during the various modes of the landing and take-off cycle; 
the time spent in each mode of the LTO (taxi/idle-out, takeoff, climb-
out, approach, and taxi/idle-in); the concentration of lead in the 
fuel; and the retention of lead in the engine and oil. The equation 
used to calculate airport-specific lead emissions during the LTO cycle 
is below, followed by a description of each of the input parameters.
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    \103\ EDMS is available online at: http://www.faa.gov/about/office_org/headquarters_offices/aep/models/edms_model/.
    \104\ U.S. Environmental Protection Agency (2008) Lead Emissions 
from the Use of Leaded Aviation Gasoline in the United States, 
Technical Support Document. EPA420-R-08-020. Available online at: 
http://www.epa.gov/otaq/aviation.htm.
[GRAPHIC] [TIFF OMITTED] TP28AP10.017

    Piston-engine LTO: Most piston-engine aircraft fall into the 
categories of either GA or AT. Some GA and AT activity is conducted by 
turboprop and turbojet aircraft which do not use leaded avgas. There 
are no national databases that provide airport-specific LTO activity 
data for piston-engine aircraft separately from turbojet and turboprop 
aircraft. The fraction of GA and AT aircraft that use piston engines 
will vary by airport. However, in the absence of airport-specific data, 
EPA calculated a national default estimate using FAA's GA and AT 
Activity (GAATA) Survey.\105\ The 2005 GAATA Survey reports that 
approximately 72% of all GA and AT LTOs are from piston-engine aircraft 
which use avgas, and about 28% are turboprop and turbojet powered which 
use jet fuel, such as Jet A.\106\ Lead is not added to jet fuel. 
Therefore, to calculate piston-engine aircraft LTO as input for this 
equation, the total GA plus AT LTOs are multiplied by 0.72.
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    \105\ The FAA GAATA is a database collected from surveys of 
pilots flying aircraft used for general aviation and air taxi 
activity. For more information on the GAATA, see Appendix A, online 
at: http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/.
    \106\ There are about 194,000 piston-engine aircraft in the U.S. 
general aviation and air taxi fleet (175,000 single-engine and 
19,000 twin-engine aircraft) according to FAA's 2005 GAATA Survey.
---------------------------------------------------------------------------

    Avgas use (gal/LTO): Piston-engine aircraft can have either one or 
two engines. EDMS version 5.0.2 contains information on the amount of 
avgas used per LTO for some single and twin-engine aircraft. The 
proportion of piston-engine LTOs conducted by single- versus twin-
engine aircraft was taken from the FAA's GAATA Survey for 2005 (90% of 
LTOs are conducted by aircraft having one engine and 10% of LTOs by 
aircraft having two engines). Since twin-engine aircraft have higher 
fuel consumption rates than those with single engines, a weighted 
average LTO fuel usage rate was established to apply to the population 
of piston-engine aircraft as a whole. For the single-engine aircraft, 
the average amount of fuel consumed per LTO was determined from the six 
types of single piston-engine aircraft within EDMS.\107\ This was 
accomplished by averaging the single-engine EDMS outputs for fuel 
consumed per LTO using the EDMS scenario property of ICAO/USEPA 
Default--Times in Mode (TIM), with a 16 minute taxi-in/taxi-out time 
according to EPA's Procedures for Emission Inventory Preparation, 
Volume IV: Mobile Sources, 1992.\108\ This gives a value of 16.96 
pounds of fuel per LTO (lbs/LTO). Next, the average single-engine 
consumption rate was divided by the average density of 100LL avgas, 6 
pounds per gallon (lbs/gal), producing an average fuel usage for 
single-engine piston aircraft of 2.83 gallons per LTO (gal/LTO). This 
same calculation was performed for the two twin-engine piston aircraft 
within EDMS, producing an average LTO fuel usage rate for twin-engine 
piston aircraft of 9.12 gal/LTO.
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    \107\ EPA understands that EDMS 5.0.2 has a limited list of 
piston engines, but these are currently the best data available.
    \108\ U.S. Environmental Protection Agency (1992) Procedures for 
Emission Inventory Preparation, Volume IV: Mobile Sources, EPA-450/
4-81-026d (Revised).
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    Using these single- and twin-engine piston aircraft fuel 
consumption rates, a weighted average fuel usage rate per LTO was 
computed by multiplying the average fuel usage rate for single-engine 
aircraft (2.83 gal/LTO) by the fleet percentage of single-engine 
aircraft LTOs (90%). Next, the twin-engine piston aircraft average fuel 
usage rate (9.12 gal/LTO) was multiplied by the fleet percentage of 
twin-engine aircraft LTOs (10%). By summing the results of the single- 
and twin-engine aircraft usage rates, the overall weighted average fuel 
usage rate per LTO of 3.46 gal/LTO is obtained.
    Concentration of lead in fuel, [Pb]: The maximum lead concentration 
specified by ASTM for 100LL is 0.56 grams per liter or 2.12 grams per 
gallon. This amount of lead is normally added to assure that the 
required lean and rich mixture knock values are achieved. As noted 
above, 100 Octane (containing 1.12 grams of lead per liter or 4.24 
grams of lead per gallon) is used by a small number of piston-engine 
aircraft. We currently do not include estimates of lead emissions using 
100 Octane and we are requesting comment on the airport facilities 
where 100 Octane is used and the LTO activity associated with the use 
of this fuel.
    Retention of lead in engine and oil (1-Pb Retention): Recent data 
collected from aircraft piston engines operating on leaded avgas 
suggests that about 5% of the lead from the fuel is retained in the 
engine and engine oil.\109\ Thus the emitted fraction is 0.95.
---------------------------------------------------------------------------

    \109\ The information used to develop this estimate is from the 
following references: (a) Todd L. Petersen, Petersen Aviation, Inc, 
Aviation Oil Lead Content Analysis, Report Number EPA 1-2008, 
January 2, 2008, available at William J. Hughes Technical Center 
Technical Reference and Research Library at http://actlibrary.tc.faa.gov/ and (b) E-mail from Theo Rindlisbacher of 
Switzerland Federal Office of Civil Aviation to Bryan Manning of 
U.S. EPA, regarding lead retained in engine, September 28, 2007.
---------------------------------------------------------------------------

    Multiplying the lead concentration in 100LL avgas by the weighted 
average fuel usage rate produces an overall average value of 7.34 grams 
of lead per LTO (g Pb/LTO) for piston engines: 3.46 gal/LTO x 2.12 g 
Pb/gal = 7.34 g Pb/LTO. The denominator is a unit conversion factor 
used to express the lead inventory in units of short tons.
    Applying these parameters in the equation above yields the 
following equation:

[[Page 22455]]

[GRAPHIC] [TIFF OMITTED] TP28AP10.018

which simplifies to: Pb = (piston-engine LTO) (7.7 x 10-6 
short tons) or 7 grams of lead per LTO where piston-engine LTO = (GA 
LTO + AT LTO)(0.72). EPA used similar methods to estimate lead 
emissions from piston-engine powered helicopters which are described 
separately.\110\ We currently estimate there are 6 grams of lead 
emitted by piston-engine helicopters per LTO.
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    \110\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to 
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline 
Lead Emissions in the 2008 NEI.'' pp.8-9.
---------------------------------------------------------------------------

    Lead emitted during the LTO cycle is assigned to the airport 
facility where the aircraft operations occur.\111\ FAA's Office of Air 
Traffic provides a complete listing of operational airport facilities 
in the National Airspace System Resources (NASR) database.\112\ In 
2008, there were 19,896 airport facilities in the U.S., the vast 
majority of which are expected to have activity by piston-engine 
aircraft that operate on leaded avgas. There are seven types of airport 
facilities: airports, balloonports, seaplane bases, gliderports, 
heliports, stolports,\113\ and ultralight facilities. Among these, 
balloonports are the only facilities not expected to have piston-engine 
aircraft activity.
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    \111\ An aircraft operation is defined as any landing or take-
off event, therefore, to calculate LTOs, operations are divided by 
two. Most data sources from FAA report aircraft activity in numbers 
of operations which, for the purposes of calculating lead emissions 
using the method described in the TSD, need to be converted to LTO 
events.
    \112\ An electronic report can be generated from the NASR 
database and is available for download from the Internet at the 
following Web site. http://www.faa.gov/airports_airtraffic/airports/airport_safety/airportdata_5010/. This database is 
updated every 56 days.
    \113\ Stolport is an airport designed with STOL (Short Take-Off 
and Landing) operations in mind, normally having a short single 
runway.
---------------------------------------------------------------------------

    Preparing airport-specific lead inventories requires information 
regarding LTO activity.
    These activity data are reported to the FAA for only a small subset 
of the approximately 20,000 facilities in the U.S. EPA obtains LTO 
information for approximately 3,400 facilities from FAA's Terminal Area 
Forecast (TAF) database that is prepared by FAA's Office of Aviation 
Policy and Plans.\114\ The TAF database currently includes information 
for airports in FAA's National Plan of Integrated Airport Systems 
(NPIAS), which identifies airports that are significant to national air 
transportation. For airports not listed in the TAF, operations data are 
obtained from the NASR database, where available. Operations data 
provided by the NASR database may be self-reported by airport operators 
through data collection accomplished by airport inspectors who work for 
the State Aviation Agency, or operations data can be obtained through 
other means.\115\
---------------------------------------------------------------------------

    \114\ http://aspm.faa.gov/main/taf.asp.
    \115\ In the absence of updated information from States, local 
authorities or Tribes, we are using the LTO data provided in the FAA 
database.
---------------------------------------------------------------------------

    We are using the January 15, 2009 version of the NASR database to 
evaluate airport lead emissions inventories for 2008. Using the TAF 
database as the primary source of LTO information and the NASR as a 
secondary source, we have LTO activity data for approximately 5,600 
airport facilities. There are approximately 14,000 facilities in the 
NASR database for which there are no LTO activity data.\116\ We 
developed methods based on previous work conducted by the FAA to 
estimate LTO activity at the remaining airport and heliport facilities. 
We are requesting comment on these methods which are described here 
briefly. The details regarding the method described here are available 
in the docket.\117\
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    \116\ No Commuter, GA Itinerant, GA Local, or Air Taxi 
operations data.
    \117\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to 
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline 
Lead Emissions in the 2008 NEI.''
---------------------------------------------------------------------------

    The FAA has used regression models to estimate operations at 
facilities where operations data are not available.118 119 
In this work and other work, FAA identified characteristics of small 
towered airports for which there were statistically significant 
relationships with operations at these airports.\120\ Regression models 
based on the airport characteristics were then used to estimate general 
aviation operations for a set of non-towered airports. The airport 
characteristics identified by the FAA and used to estimate general 
aviation operations at small airports include: the number and type of 
aircraft based at the facility (i.e., ``based aircraft''), population 
in the vicinity of the airport, airport regional prominence, per capita 
income, region of the country, and the presence of certificated flight 
schools. We were able to obtain data from the NASR and the U.S. Census 
Bureau to evaluate relationships between several airport 
characteristics and LTO activity. LTO estimates were derived using 
different models depending on data availability.
---------------------------------------------------------------------------

    \118\ Federal Aviation Administration, Office of Aviation Policy 
and Plans, Statistics and Forecast Branch. (July 2001) Model for 
Estimating General Aviation Operations at Non-Towered Airports Using 
Towered and Non-towered Airport Data. Prepared by GRA, Inc.
    \119\ Hoekstra, M. (April 2000) Model for Estimating General 
Aviation Operations at Non-Towered Airports. Prepared for FAA Office 
of Aviation Policy and Plans.
    \120\ GRA, Inc. ``Review of TAF Methods,'' Final Report, 
prepared for FAA Office of Aviation Policy and Plans under Work 
Order 45, Contract No. DTFA01-93-C-00066, February 25, 1998.
---------------------------------------------------------------------------

    The number of based aircraft and county population in which the 
airport is located were the most highly significant and positive 
regressors to LTO activity that our analysis provided.\121\ The 
regression equation for based aircraft and county population is: LTOs = 
1248 + 203.04*Aircraft + 0.0019*County Population with an R\2\ = 0.64. 
For approximately 7,800 facilities that do not report LTO activity to 
FAA, we used based aircraft and county population to estimate activity. 
We request comment on the method we are using to estimate LTO activity 
at these airport facilities.
---------------------------------------------------------------------------

    \121\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to 
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline 
Lead Emissions in the 2008 NEI.''
---------------------------------------------------------------------------

    To estimate LTO activity at the airport facilities that do not 
report based aircraft, we used a regression equation based on county 
population and region of the country. The regression equation using 
county population and regression of the country is: LTOs = 6200.2 + 
0.0087*county population--175.07*West State - 5567.3*Alaska + 
854.83*Northeast with an R\2\ = 0.15. This equation has a low 
correlation coefficient and we are exploring additional options for 
estimating LTO activity at these facilities for which very little 
information is reported to the FAA. We request comment on applying the 
regression equation above and alternative methods to estimate LTO 
activity at these facilities.
    For heliports, which comprise approximately 5,500 facilities in the 
NASR database, we had insufficient information on which to develop a 
regression equation and are currently using the median of activity (141 
LTOs/year) at heliports for which we have LTO activity data. 
Nationally, 25% of helicopters are piston-engine powered and therefore 
use leaded avgas. The FAA and EPA have limited information

[[Page 22456]]

regarding the specific heliports that have activity by piston-engine 
helicopters. We are requesting information regarding heliport 
facilities at which piston-engine powered aircraft operate and the 
activity of these aircraft.
    The draft 2008 NEI is the first inventory for which we are 
implementing the use of LTO-based lead estimates at almost 20,000 
airport facilities and we are expecting State, local and Tribal air 
agency review of these data to improve our current estimates. The 
specific information on which we are requesting data include: (1) The 
fraction of GA and AT LTO activity reported to FAA that is conducted by 
piston-engine versus jet-engine powered aircraft, (2) airport-specific 
LTO activity for single- versus twin-engine piston-powered aircraft, 
(3) fuel consumption rates for the piston-engine aircraft operating at 
each airport, (4) the time spent in each mode of operation including 
run-up checks conducted by piston-engine aircraft prior to take-off, 
and (5) the concentration of lead in fuel delivered to individual 
airports. Methods for providing information to EPA as part of the 
review process involved in finalizing the 2008 NEI are available.\122\
---------------------------------------------------------------------------

    \122\ All documentation for use in preparing 2008 emission 
inventories can be found on the NEI/EIS Implementation Web site: 
http://www.epa.gov/ttn/chief/net/neip/index.html.
---------------------------------------------------------------------------

    The discussion above pertains only to lead emissions during the LTO 
cycle. Lead emitted outside the LTO cycle occurs during aircraft cruise 
mode and portions of the climb-out and approach modes. This part of an 
aircraft operation emits lead at various altitudes as well as close to 
and away from airports. We are developing methods to estimate lead 
emissions outside the LTO cycle which we anticipate will be available 
in 2010.

B. Projections for Future Growth

    The FAA publishes an annual forecast of the number of piston-engine 
powered aircraft, hours flown, the consumption of avgas, the numbers of 
pilots and student pilots.\123\ The most recent forecast is for the 
years 2009 through 2025. The General Aviation Manufacturers Association 
(GAMA) reproduces the FAA forecast in their annual statistical 
databook.\124\ According to the GAMA summary, the number of active 
single-engine piston-powered aircraft is projected to increase annually 
at a 0.5% growth rate, with the aircraft population increasing from 
144,220 in 2008 to 157,400 in 2025. The number of active twin-engine 
piston-powered aircraft is projected to decrease 0.9% annually, with 
aircraft population decreasing from 18,385 in 2008 to 15,650 in 2025. 
The piston-powered helicopter population is expected to grow 4.7% 
annually from a population of 3,970 in 2008 to 8,295 in 2025.
---------------------------------------------------------------------------

    \123\ FAA Aerospace Forecast Fiscal Years 2009-2025. Available 
online at: http://www.faa.gov/data_research/aviation.
    \124\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook and Industry Outlook, pp.51-55. 
Available online at: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
---------------------------------------------------------------------------

    The FAA forecast predicts the number of hours flown in single-
engine piston-powered aircraft is projected to increase 0.5% yearly 
from 2008 to 2025); the number of hours flown in twin-engine piston-
powered aircraft is projected to decrease 1.5% annually and the number 
of hours flown in piston-powered rotocraft is projected to increase 
3.9% annually. The changes in numbers of piston aircraft and hours 
flown is generally reflected in the consumption of leaded avgas. For 
the years 2008 through 2025, DOT's FAA estimates no change in the 
volume of leaded avgas consumed by single-engine aircraft in the U.S. 
(204 million gallons in 2008 and 2025), a 1.9% decrease in leaded avgas 
consumed by multi-engine aircraft (from a baseline of 108 million 
gallons in 2008 to 78 million gallons in 2025), and a 3.8% annual 
increase in the volume of leaded avgas consumed by piston-powered 
helicopters (from a baseline of 13 million gallons in 2008 to 24 
million gallons in 2025). For 2025, the forecast volume of leaded avgas 
is 348 million gallons. Consumption of this volume of fuel would 
release 773 tons of lead to the air in 2025.
    The number of active pilots flying general aviation aircraft 
(excluding air transport pilots) is projected to be slightly over half 
a million in 2025, representing a yearly increase of 0.7% over the 
forecast period.\125\ The student pilot population is forecast to 
increase at a slightly higher rate of 1.0% yearly for a 2025 total 
slightly over 100,000. Private pilots and sport pilots are also 
projected to increase yearly (0.2% yearly increase in the number of 
private pilots). EPA is requesting comments on the forecast information 
presented in this section and on the uncertainty in these projections.
---------------------------------------------------------------------------

    \125\ Except for sport pilots, an active pilot is a person with 
a pilot certificate with a valid medical certificate. Source: FAA 
2008-2025 Aerospace Forecast.
---------------------------------------------------------------------------

IV. Lead Concentrations in the Vicinity of Airports

    This section summarizes information regarding the chemical and 
physical properties of lead emitted by piston-engine aircraft and 
monitoring and modeling studies regarding ambient and soil lead 
concentrations in the vicinity of airports where piston-engine aircraft 
operate.

A. Chemical and Physical Properties of Lead Emitted by Piston-Engine 
Aircraft

    Information regarding lead emissions from engines operating on 
leaded fuel is summarized in prior AQCDs for Lead.126 127 
The chemical form of lead added to avgas (i.e., tetraethyl lead) and 
the lead scavenger, ethylene dibromide, are the same compounds used in 
leaded gasoline for motor vehicles in the past. Therefore, the summary 
of the science regarding emissions of lead from motor vehicles 
presented in the 1997 and 1986 AQCD for Lead are relevant to 
understanding some of the properties of lead emitted from piston-engine 
aircraft. In addition, the Swiss Federal Office of Civil Aviation 
(FOCA) published a study of piston-engine aircraft emissions including 
measurements of lead.\128\
---------------------------------------------------------------------------

    \126\ U.S. Environmental Protection Agency (1977) Air Quality 
Criteria for Lead. Research Triangle Park, NC: Office of Health and 
Environmental Assessment, Environmental Criteria and Assessment 
Office; EPA report no. EPA-600/8-77-017. Available at: http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_pr.html.
    \127\ U.S. Environmental Protection Agency (1986) Air Quality 
Criteria for Lead. Research Triangle Park, NC: Office of Health and 
Environmental Assessment, Environmental Criteria and Assessment 
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available at: 
http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_pr.html.
    \128\ Federal Office of Civil Aviation Environmental Affairs 
(2007) Aircraft Piston Engine Emissions Summary Report. 33-05-003 
Piston Engine Emissions--Swiss FOCA--Summary. Report--070612--rit. 
Available online at: http://www.bazl.admin.ch.
---------------------------------------------------------------------------

    When leaded avgas is combusted, the lead is oxidized to form lead 
oxide. In the absence of a lead scavenger in the fuel, lead oxide can 
collect on the valves and spark plugs and if the deposits become thick 
enough, the engine can be damaged. Ethylene dibromide reacts with the 
lead oxide, converting it to brominated lead and lead oxybromides. 
These halogenated forms of lead are volatile at the high temperatures 
experienced under combustion conditions and are therefore exhausted 
from the engine along with the other combustion by-products.\129\ Upon 
cooling to ambient temperatures these brominated lead compounds are 
converted to particulate matter. In addition to lead halides, ammonium 
salts of lead halides were also emitted by motor vehicles.\130\ Lead 
halides

[[Page 22457]]

undergo compositional changes upon cooling and mixing with the ambient 
air as well as during transport; the water-solubility of these lead-
bearing particles increases with a shift toward smaller mean particle 
size (USEPA 1977, Section 6.2.2.1). Lead halides from automobile 
exhaust break down rapidly in the atmosphere, via redox reactions in 
the presence of atmospheric acids (AQCD for Lead, page E-17).
---------------------------------------------------------------------------

    \129\ ChevronTexaco (2006) Aviation Fuels Technical Review pp. 
64-65. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
    \130\ U.S. Environmental Protection Agency (1986) Air Quality 
Criteria for Lead. Volume 2 Section Chapters 5 & 6. Research 
Triangle Park, NC: Office of Health and Environmental Assessment, 
Environmental Criteria and Assessment Office; EPA report no. EPA-
600/8-83/028aF-dF. 4v. Available from: NTIS, Springfield, VA; PB87-
142378.
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    A small fraction of uncombusted alkyl lead was measured in the 
exhaust of motor vehicles operating with leaded gasoline and is 
therefore likely to be present in the exhaust from piston-engine 
aircraft.\131\ Alkyl lead is the general term for organic lead 
compounds and includes the lead additives tetramethyl lead and 
tetraethyl lead. Tetraethyl lead is a highly volatile compound and 
therefore, a portion of tetraethyl lead in fuel exposed to air will 
partition into the vapor phase. Tetraethyl lead can enter the 
atmosphere from avgas distribution systems, refueling operations, fuel 
check pre-flight procedures and evaporative losses from the 
aircraft.\132\ Tetraethyl lead has an atmospheric residence time 
ranging from a few hours to a few days. Tetraethyl lead reacts with the 
hydroxyl radical in the gas-phase to form a variety of products that 
include ionic trialkyl lead, dialkyl lead and metallic lead. Trialkyl 
lead is slow to react with the hydroxyl radical and is quite persistent 
in the atmosphere (AQCD for Lead, page 2-5).
---------------------------------------------------------------------------

    \131\ U.S. Environmental Protection Agency Persistent, 
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT 
national action plan for alkyl-Pb. Washington, DC. Available online 
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
    \132\ U.S. Environmental Protection Agency Persistent, 
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT 
national action plan for alkyl-Pb. Washington, DC. p. 12. Available 
online at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
---------------------------------------------------------------------------

    Particles emitted by piston-engine aircraft are in the submicron 
size range (less than one micron in diameter). The Swiss FOCA reported 
the mean particle diameter of particulate matter emitted by one single-
engine piston-powered aircraft ranged from 0.049 to 0.108 microns under 
different power conditions. The particle number concentration ranged 
from 5.7 x 10\6\ to 8.6 x 10\6\ particles per cm\3\ and using a 
specific density for soot of 1.2, the authors estimated the mass 
concentration of particulate emissions as approximately 10,000 [mu]g/
m\3\. The authors noted that these particle emission rates are 
comparable to those from a typical diesel passenger car engine without 
a particle filter (FOCA, Section 2.2.3.a).
    A significant fraction of particles in the submicron size range are 
deposited and retained in the lower respiratory system of humans and 
animals (AQCD for PM, page 6-108).\133\ The 1986 AQCD for Lead 
concludes that lead deposited in the lower respiratory tract is totally 
absorbed (USEPA 1986, page 10-2).
---------------------------------------------------------------------------

    \133\ U.S. Environmental Protection Agency (2004) Air Quality 
Criteria for Particulate Matter (AQCD). Volume II Document No. 
EPA600/P-99/002bF. Washington, DC: U.S. Environmental Protection 
Agency. Available online at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903.
---------------------------------------------------------------------------

    Due to their small size (i.e., typically less than one micron in 
diameter), lead-bearing particles emitted by piston engines may 
disperse widely in the environment. However, lead emitted during LTO, 
particularly during ground-based operations such as start-up, idle, 
preflight run-up checks, taxi and take-off may deposit to the local 
environment. Meteorological factors (e.g., wind speed, convection, 
rain, humidity) will influence local deposition rates. As discussed in 
the overview section of this ANPR, many airports in the country have 
been home to piston-engine operations for decades, including years when 
lead concentrations in avgas were twice as high as current levels. We 
seek comment on the chemical and physical form of lead emissions from 
piston-engine aircraft as well as dispersion and deposition patterns 
that may influence the risk for local-scale impacts.

B. Summary of Airport Lead Monitoring and Modeling Studies

    Lead concentrations in ambient air have been reported for samples 
collected on or near five airports: the Santa Monica municipal airport 
in Santa Monica, CA, the Van Nuys airport in Van Nuys, CA, the Chicago 
O'Hare airport in IL, the Toronto Buttonville municipal airport in 
Ontario, Canada, and the Destin airport in Destin, 
FL.134 135 136 137 138 Air quality modeling of lead 
emissions from piston-engine aircraft has been conducted as part of 
EPA's National Air Toxics Assessment and in one 
study.139 140 As discussed in Section VI.A of this ANPR, 
State and local agencies are initiating lead monitoring at four 
airports in 2010 that will provide additional information regarding the 
air quality impact of lead emissions from piston-engine aircraft.
---------------------------------------------------------------------------

    \134\ South Coast Air Quality Management District (2007) 
Community-Scale Air Toxics Monitoring--Sun Valley Neighborhood and 
General Aviation Airports. Presented by Dr. Philip Fine at the U.S. 
EPA Air Toxics Data Analysis Workshop--Chicago, IL. October 2-4, 
2007.
    \135\ Illinois Environmental Protection Agency Bureau of Air 
(2002) Chicago O'Hare Airport Air Toxic Monitoring Program June-
December, 2000.
    \136\ Environment Canada (2000) Airborne Particulate Matter, 
Lead and Manganese at Buttonville Airport. Toronto, Ontario, 
Canada:Conor Pacific Environmental Technologies for Environmental 
Protection Service, Ontario Region.
    \137\ Tetra Tech, Inc. (2007) Destin Airport Air Sampling 
Project Executive Summary. Prepared for City of Destin, Florida.
    \138\ Tetra Tech, Inc. (2008) Destin, Florida Airport Sampling 
Report. October 2008. Prepared for City of Destin, Florida.
    \139\ Piazza, B for the Los Angeles Unified School District 
Environmental Health and Safety Branch (1999) Santa Monica Municipal 
Airport: A Report on the Generation and Downwind Extent of Emissions 
Generated from Aircraft and Ground Support Operations. Report 
Prepared for The Santa Monica Airport Working Group. Available 
online at: http://yosemite.epa.gov/oar/CommunityAssessment.nsf/
6ce396ab3fa98ee485256db0004acd94/$FILE/Santa--Monica.pdf
    \140\ U.S. Environmental Protection Agency (2009) 2002 National-
Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn/atw/nata2002/index.html.
---------------------------------------------------------------------------

1. Summary of Airport Lead Monitoring Studies
    The ambient air monitoring studies reporting lead concentrations on 
and near airport property served many purposes and therefore used 
different criteria for determining sample locations, sample durations, 
sample collection methods, and collection of important metadata (e.g., 
activity of piston-engine aircraft and aircraft engine type). This 
section summarizes results from these studies.
    Ambient monitoring studies at and near airports indicate that lead 
levels in ambient air at or near airports with piston-engine activity 
are higher than lead levels in areas not directly influenced by a lead 
source. The study at the Santa Monica Airport \141\ is the only study 
to date in which a lead monitor was sited at an area of anticipated 
maximum concentration for a period of time that provides ambient 
concentrations relevant for comparison to the Lead NAAQS.\142\ In this 
study where monitors were placed in

[[Page 22458]]

locations to identify the gradient in lead concentrations with distance 
from piston-engine activity, ambient lead increased with increasing 
proximity to the airport. Lead monitors were located at seven sites 
around the Santa Monica Airport for two three-month periods, in Spring 
2006 and Winter 2006-2007. At the monitor placed near the runway blast 
fence (i.e., the maximum impact site) on the Santa Monica Airport 
property, the quarterly average concentrations of lead in total 
suspended particulate matter (TSP) were 0.08 (winter) and 0.10 (spring) 
[mu]g/m\3\.\143\ The maximum quarterly average concentration of lead in 
total suspended particulate matter (TSP) was 0.10 [mu]g/m\3\, 67% of 
the 2008 Lead NAAQS of 0.15 [mu]g/m\3\. This suggests that ambient air 
lead concentrations at similar airports with more piston-engine 
activity than the Santa Monica Airport may be higher, and could further 
approach or exceed 0.15 [mu]g/m\3\. At a neighborhood site, 70 meters 
in the prevailing downwind direction from the maximum impact site, 
quarterly average concentrations of lead in TSP were 0.02 [mu]g/m\3\ 
(winter) and 0.03 [mu]g/m\3\ (spring).\144\ At a distance of one 
kilometer in the prevailing downwind direction from the maximum impact 
site, lead concentrations were 0.004 [mu]g/m\3\ and 0.008 [mu]g/m\3\ in 
winter and spring, respectively (these concentrations are considered 
the background lead concentration). The study conducted at the Santa 
Monica Airport reported concentrations of ambient lead that were 
highest at on- and near airport areas downwind from the emissions of 
piston-engine aircraft. These data suggest that piston-engine activity 
can increase ambient lead concentrations in downwind neighborhood 
sites, resulting in levels that are four to five times higher than 
background levels and maximum impact site concentrations that are up to 
25 times higher than background lead levels.\145\
---------------------------------------------------------------------------

    \141\ South Coast Air Quality Management District (2007) 
Community-Scale Air Toxics Monitoring--Sun Valley Neighborhood and 
General Aviation Airports. Presented by Dr. Philip Fine at the U.S. 
EPA Air Toxics Data Analysis Workshop--Chicago, IL. October 2-4, 
2007. This presentation includes lead monitoring data collected at 
and near the Santa Monica Airport and the Van Nuys Airport.
    \142\ As with other lead sources, source-oriented monitors for 
airports should be sited in ambient air at the location of predicted 
maximum lead concentration. Typically, the location of maximum lead 
concentration will be downwind of the take off strip near the 
``blast fence.'' http://www.epa.gov/ttnamti1/files/ambient/pb/NetworkDesignQA.pdf.
    \143\ A low-volume sampler was used at this site which EPA 
expects would yield comparable results to a high-volume sampler, the 
latter of which is the current method used to collect samples for 
comparison with the Lead NAAQS.
    \144\ These distances were measured using Google Earth Pro 
software.
    \145\ EPA notes that additional information regarding this study 
at the Santa Monica Airport may become available. If additional 
information does become available, EPA will take this information 
into account in the NPRM.
---------------------------------------------------------------------------

    As with other emissions from internal combustion engines, lead 
emitted by piston-engine aircraft are largely in the submicron and even 
ultrafine size fraction; therefore, analogies to gradients in ultrafine 
PM are relevant. As summarized in EPA's 2009 Integrated Science 
Assessment for Particulate Matter, ultrafine particulate number counts 
decrease exponentially with distance from roadways.\146\ A recent study 
at the Santa Monica Airport reported increased ultrafine PM in a 
neighborhood downwind from aircraft operations that were conducted by 
jet and piston-engine aircraft.\147\ The EPA is conducting modeling and 
monitoring studies to further evaluate the gradient in lead 
concentrations with distance from airports (see Section VI.B of this 
ANPR).
---------------------------------------------------------------------------

    \146\ U.S. Environmental Protection Agency (2009) Integrated 
Science Assessment for Particulate Matter. Second External Review 
Draft. EPA/600/R-08/139B. p. 3-110. Available online at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210586.
    \147\ Hu, S., Fruin, S., Kozawa, K., Mara, S., Winer, A.M., 
Paulson, S.E. (2009) Aircraft Emission Impacts in a Neighborhood 
Adjacent to a General Aviation Airport in Southern California. 
Environ. Sci. Technol. 43:8039-8045.
---------------------------------------------------------------------------

    At the Van Nuys Airport, lead monitoring in ambient air was 
conducted at six sites for two three-month periods. Lead monitoring for 
this study included locations of ambient air on airport property. 
However, monitors were not sited in the area anticipated to experience 
the maximum impact from piston-engine aircraft emissions. The 
monitoring site that was in closest proximity to the maximum impact 
area was more than one kilometer downwind from the maximum impact 
site.\148\ The highest quarterly concentration of lead observed at the 
Van Nuys Airport was at the monitor located over one kilometer away 
from the maximum impact site and the lead concentration at this site 
was 0.03 [mu]g/m\3\ which was four-fold higher than the regional 
background level of 0.008 [mu]g/m\3\ measured during the same time 
period at a site over 2.5 kilometers from the north end of the Van Nuys 
Airport.
---------------------------------------------------------------------------

    \148\ These distances were measured using Google Earth Pro 
software. Prevailing wind direction, which determines the direction 
in which the majority of aircraft depart, is provided in the SCAQMD 
presentation of these data.
---------------------------------------------------------------------------

    At the Toronto Buttonville Municipal Airport, ten 24-hour 
PM10 samples were collected at four sites at the airport (as 
close as 15 meters from the runway) and one urban background site in 
downtown Toronto (located about 10 kilometers west, southwest of the 
airport). PM10 is particulate matter less than ten microns 
in aerodynamic diameter. The average lead concentration among the 
airport monitors (which includes three samples that were taken for less 
than a 12-hour period), was 0.03 [mu]g/m\3\ and the maximum 24-hour 
lead concentration was 0.13 [mu]g/m\3\. One sample, collected for 11 
hours, measured 0.30 [mu]g/m\3\. The maximum concentration observed 
over a 24-hour period at the airport during this study (0.13 [mu]g/
m\3\) was 11 times higher than the lead concentration reported for the 
downtown Toronto, Canada background site during the same time period 
(0.012 [mu]g/m\3\).\149\ The average lead concentration reported for 
the downtown Toronto site was 0.007 [mu]g/m\3\. The total particulate 
matter mass in PM10 was also measured in this study, and at 
the airport, the average mass of lead in PM10 was 0.15% of 
the total PM10 mass. At the downtown Toronto site, the 
average mass of lead in PM10 was 0.04% of the total 
PM10 mass. The study reported that the use of leaded avgas 
at the airport was evident in enhanced airborne lead levels.
---------------------------------------------------------------------------

    \149\ Average concentrations reported in this study include 
three days of short-duration sampling so the average is not used for 
comparison here.
---------------------------------------------------------------------------

    Lead and other hazardous air pollutants were measured at sites 
upwind and downwind of the Chicago O'Hare Airport on sixteen days 
during the period from June through December, 2000. In order to assess 
the potential impact of airport operations on ambient concentrations of 
lead and other pollutants in areas adjacent to airport property, two 
monitoring sites were deployed on different sides of the airport: one 
in Bensenville, IL and the other in Schiller Park, IL. For five days 
during the sampling campaign, the prevailing wind direction provided 
samples that were collected simultaneously upwind and downwind of the 
airport. Lead concentrations measured at the downwind site on these 
five days were, on average, 88% higher than lead concentrations 
measured at the upwind site. Lead concentrations at the upwind site 
over the five days averaged 0.016 [mu]g/m\3\ and downwind 
concentrations averaged 0.030 [mu]g/m\3\. This study demonstrates the 
potential for operations on airport property to impact ambient lead 
concentrations downwind.
    Lead TSP samples were collected for four days in April 2007 and for 
three days in July 2008 near the Destin Airport in Destin, FL. Twelve-
hour TSP samples (AM and PM) were collected at four residential 
locations ranging from 200 meters to 400 meters from the runway at the 
Destin Airport and at two urban background locations which were 1.4 
kilometers and 2.7 kilometers from the airport.\150\ The average lead 
concentration among the four residential locations was 0.004 [mu]g/m\3\ 
and 0.005 [mu]g/m\3\ in April and July, respectively, and the average 
urban

[[Page 22459]]

background lead concentration was 0.003 and 0.004 [mu]g/m\3\ in April 
and July, respectively.
---------------------------------------------------------------------------

    \150\ These distances were measured using Google Earth Pro 
software.
---------------------------------------------------------------------------

    In addition to these airport-specific studies, authors evaluating 
ambient lead concentrations collected as part of the Interagency 
Monitoring of Protected Visual Environments (IMPROVE) network and the 
National Oceanic and Atmospheric Administration (NOAA) monitoring sites 
reported a weekend increase in ambient lead that the authors attributed 
to weekend increases in piston-engine powered general aviation 
activity.\151\ At some airports, piston-engine aircraft activity 
conducted for recreational purposes can increase greatly on weekends 
and can also change seasonally with weather conditions. These peaks in 
activity are important to capture because they may have a strong 
influence on long-term average concentrations in an area. However, the 
current database for ambient lead concentrations at maximum impact 
sites at airports is severely limited and does not allow us to 
quantitatively evaluate the influence of this variability in activity 
on ambient lead concentrations.
---------------------------------------------------------------------------

    \151\ Murphy, D.M., Capps, S.L., Daniel, J.S., Frost, G.J., and 
White, W.H. (2008) Weekly patterns of aerosol in the United States. 
Atmos. Chem. Phys., 8, 2729-2739.
---------------------------------------------------------------------------

    We have identified no studies evaluating the potential contribution 
of piston-engine aircraft emissions on vegetation. We have identified 
only one study that reports soil concentrations on airport property 
where piston-engine aircraft are active. The air monitoring study 
conducted at the Toronto Buttonville airport in Ontario, Canada 
reported lead concentrations in soil samples collected at eight 
locations at the airport and two locations at the urban background 
site. Soil samples that were collected at the Toronto Buttonville 
airport had lead concentrations ranging from 22-46 [mu]g/g which was 
not substantially higher than the lead concentrations in soil samples 
at the two urban background sites (29 and 31 [mu]g/g). We are seeking 
comments on the potential for piston-engine aircraft emissions to 
impact local soil lead concentrations.
2. Summary of Airport Lead Modeling Studies
    Lead emissions from piston-engine aircraft at 3,410 airports were 
included in the recently released 2002 National Air Toxics Assessment 
(NATA) as nonroad sources of lead.\152\ Ambient lead concentrations and 
exposures to lead are modeled for area, point and nonroad sources. 
Nonroad sources include only lead emissions from piston-engine 
aircraft. Lead emission rates are based on the lead concentration in 
fuel and not direct emission measurements. For the NPRM we will 
summarize modeling results from the 2005 NATA which will incorporate 
all 20,000 airport facilities discussed in Section III of this ANPR.
---------------------------------------------------------------------------

    \152\ U.S. Environmental Protection Agency (2009) 2002 National-
Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn/atw/nata2002/tables.html.
---------------------------------------------------------------------------

    As discussed in Section VI of this ANPR, the EPA has conducted a 
study to develop a modeling approach to evaluate the local-scale 
variability in ambient lead concentrations attributable to piston-
engine activity at a case study airport. This project includes 
collection of air monitoring data for use in evaluating model 
performance. In the NPRM, we will describe the results of the modeling 
study with NATA results for this airport and previous modeling 
work.\153\
---------------------------------------------------------------------------

    \153\ Piazza, B for the Los Angeles Unified School District 
Environmental Health and Safety Branch (1999) Santa Monica Municipal 
Airport: A Report on the Generation and Downwind Extent of Emissions 
Generated from Aircraft and Ground Support Operations. Report 
Prepared for The Santa Monica Airport Working Group. Available 
online at: http://yosemite.epa.gov/oar/CommunityAssessment.nsf/
6ce396ab3fa98ee485256db0004acd94/$FILE/Santa--Monica.pdf.
---------------------------------------------------------------------------

    We are requesting comment on the availability of additional 
monitoring or modeling studies that evaluate the air quality impact of 
lead emissions from piston-engine aircraft as well as potential impacts 
on soil, house dust, surface water or other environmental media. We 
also request comment on the availability of studies that assess the 
potential public health and welfare impacts of lead emissions from 
piston-engine aircraft.

V. Exposure to Lead From Piston-Engine Aircraft and Potential for 
Impacts

    The continued use of lead in avgas by piston-engine aircraft is a 
significant source of current lead emissions to the environment. 
Piston-engine aircraft emissions of lead occur at ground level as well 
as at flying altitude. Lead from this source is thus concentrated near 
airports and is also deposited over a large geographic area potentially 
contributing to higher ambient concentrations in many communities. 
Numerous groups within the population may be at risk of exposure to 
lead in fresh emissions from piston-engine aircraft, resuspended dust 
or other routes. Further, lead accumulates in the environment posing a 
potential risk to future generations
    In this section we discuss a variety of exposure pathways and 
scenarios by which the general population and environment may 
experience an increase in lead exposure from emissions of lead by 
piston-engine aircraft. This section also describes the potential for 
public health and welfare effects from exposure to compounds associated 
with the continued use of tetraethyl lead in fuel, such as the 
contribution of lead to ambient particulate matter, emissions of 
ethylene dibromide and non-exhaust exposure to tetraethyl lead. We are 
seeking comments and information on these exposure scenarios as well as 
additional exposure pathways and scenarios.

A. Exposure to Lead Emissions From Piston-Engine Aircraft

    Piston-engine aircraft emissions of lead occur at ground level as 
well as at altitudes, resulting in areas of more concentrated ambient 
air exposure, as discussed in Section IV, and can also be distributed 
over large geographic areas due to in-flight emissions. Lead particles 
can deposit to soil, water, vegetation and other surfaces or remain 
airborne for some time following emissions. In this section we discuss 
potentially exposed populations which include people living or 
attending schools near airports and pilots. Additional pathways by 
which people and animals could be exposed to lead emissions from 
piston-engine aircraft are those associated with agricultural 
applications of these aircraft and piston-engine activity at seaport 
and inland waterways.
    Lead from aviation gasoline has been identified as a potential 
source of contamination for local communities.\154\ As described below, 
many general aviation airports are located in densely populated areas. 
GA airport facilities were typically built in sparsely populated areas, 
many of which are now heavily populated or are experiencing increased 
residential development. This development includes dense residential 
neighborhoods, schools, businesses, and recreational facilities.
---------------------------------------------------------------------------

    \154\ Levin, R.; Brown, MJ; Kashtock, ME; Jacobs, DE; Whelan, 
EA; Rodman, J; Schock, MR; Padilla, A; Sinks, T. (2008) Lead 
Exposures in U.S. Children, 2008: Implications for Prevention. 
Environ. Health Perspec. 116:1285-1293.
---------------------------------------------------------------------------

    Airports can function as a center of many forms of activity in a 
community. In EPA's initial research, EPA has found that airports are 
often surrounded by a variety of land uses including recreational sport 
facilities (e.g., baseball diamonds, soccer fields, golf courses, and 
swimming pools) and residential communities that take

[[Page 22460]]

advantage of the ease of transport and pilot training/recreation 
offered by quick access to an airport. Many airports offer on-site 
tours to the general public, educational classes, and recreational 
opportunities that can present near-source exposure scenarios. Airports 
are especially attractive to young children, and programs at some 
airports are focused on this population and provide outdoor observation 
facilities and picnic facilities for families to observe aircraft 
operations. Many general aviation airports offer instructional flying 
and/or clubs where children 14 years of age and older as well as adults 
can learn to fly in rental aircraft. Airport facilities also host 
community-friendly activities such as antique sales, fireworks 
displays, air shows and community meals. Many airport facilities 
provide activities which bring people from the general public in close 
proximity to lead emissions from piston-engine aircraft and piston-
engine helicopters. EPA is requesting information regarding national 
databases that provide information regarding recreational fields and 
community gardens in close proximity to airports.
1. Population Residing Near Airports
    To evaluate the number of people who might be exposed to elevated 
lead levels due to emissions from piston-engine aircraft, EPA 
calculated the number of people that live within one kilometer of the 
centroid of an airport.\155\ The centroid of the airport is defined 
here as the latitude and longitude coordinate provided by airports to 
FAA.\156\ These coordinates typically identify a location in the center 
of the runway or runway area. For some airports, nearby residences are 
outside the one kilometer distance from the airport centroid. This is 
the case for residences near airports that have runways that are longer 
than two kilometers and for residences near large airports such as 
those servicing primarily commercial aircraft activity. For airport 
facilities with one runway that is approximately one kilometer in 
length, this method will generally include people residing within 
approximately 500 meters from the ends of the runway and may include 
residences up to approximately 900 meters from the sides of the runway. 
The limited ambient lead monitoring data near airports presented in 
Section IV of this ANPR suggests that for some airports this analysis 
will underestimate the actual number of people potentially exposed to 
elevated levels of ambient lead from piston-engine powered aircraft. 
This is because the analysis will include very little of the nearby 
population for airports that have a large footprint. We plan to revise 
this analysis for the NPRM using a graphical interface system that will 
allow us to evaluate the number of people living within uniform 
distances of aircraft activity.
---------------------------------------------------------------------------

    \155\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to 
docket EPA-HQ-OAR-2007-0294, titled, ``Evaluation of People Living 
Within 1 km of U.S Airport Facilities.''
    \156\ Federal Aviation Administration. Airport Data (5010) & 
Contact Information, Airport Facilities Data. Retrieved on August 
13, 2009 from: http://www.faa.gov/airports/airport_safety/airportdata_5010/menu/index.cfm.
---------------------------------------------------------------------------

    Using 2000 U.S. Census Data \157\ at the block level, EPA estimates 
that 16 million people live within one kilometer of the centroid of the 
19,896 airport facilities which includes airports, seaplane bases, 
heliports, stolports, ultralight facilities and glider ports. There are 
currently 5,567 heliports in this analysis, which can be in densely 
populated areas. Fourteen of the 16 million people living within one 
kilometer of the centroid of an airport facility live within one 
kilometer of a heliport. We currently have limited information 
regarding which heliport facilities have piston-engine activity and we 
are seeking comment on piston-engine activity at heliports.
---------------------------------------------------------------------------

    \157\ Obtained from: http://www.epa.gov/ttn/fera/human_hem_censusandmet.html.
---------------------------------------------------------------------------

    There are several pathways by which people may be exposed to lead 
associated with the use of piston-engine aircraft. These include 
inhalation of ambient airborne lead as well as incidental ingestion of 
ambient lead through contact with indoor or outdoor surfaces to which 
ambient lead has deposited. Additionally, ambient lead deposited to 
outdoor soil can be tracked into interior spaces. There is also the 
potential for ingestion of lead emitted by piston engine aircraft 
emissions to deposit on edible plants and produce being cultivated in 
locations near airports. Consequently, there is the potential for 
exposure to lead emitted by piston-engine aircraft via ingestion for 
those consuming vegetables grown near airports that service piston-
engine aircraft. In addition to personal gardens, community gardens are 
sometimes sited near airports as these areas can have undeveloped 
available land. We do not have information on the potential 
significance of this exposure pathway and we are seeking comment on 
information and analyses that could inform this issue.
    In some cases, pilots and their families choose to live in close 
proximity to an airstrip. These communities intentionally placed near 
airports are known as airport communities, fly-in communities or 
residential airparks. Some residential airparks are private while 
others have public services and facilities. Some residential airparks 
are specifically designed as airport communities with driveways leading 
from aircraft hangars or tie-downs onto the airstrip, while other 
residential airparks allow apartments to be built in the airplane 
hangar. Other residential airparks are developed by the addition of a 
neighborhood immediately adjacent to a commercial airport. FAA terms 
this a ``through-the-fence'' operation.\158\ Homes are required to be 
at least 45 meters from the runway centerline and can be built along 
one or both sides of the runway.\159\ Some residential airparks provide 
taxiways for access to the runway, some provide streets separate from 
taxiways, and some share automobile and aircraft traffic on the same 
thoroughfares. A variety of resources list the location and services 
offered by residential airparks in the U.S. and estimates of the number 
of residential airparks range from 300 to 600.160 161
---------------------------------------------------------------------------

    \158\ FAA officially defines ``through-the-fence'' as those 
activities permitted by an airport sponsor through an agreement that 
permits access to the public landing area by independent entities or 
operations offering an aeronautical activity or to owners of 
aircraft based on land adjacent to, but not part of, the airport 
property. The obligation to make an airport available for the use 
and benefit of the public does not impose any requirement for the 
airport sponsor to permit ground access by aircraft from adjacent 
property. (http://www.aopa.org/whatsnew/region/airportOps0712.pdf).
    \159\ ASTM International (2005) ASTM F2507-05 Standard 
Specification for Recreational Airpark Design
    \160\ http://www.airparks.com maintains a list of airparks that 
have five or more homes/lots. The list can be updated by the public 
and as of July 31, 2009, lists 326 residential airparks.
    \161\ http://livingwithyourplane.com/about/ has a directory of 
over 600 residential airparks.
---------------------------------------------------------------------------

    In some cases, records are maintained only for those residential 
parks that have five or more homes or lots.
    Exposure modeling at the EPA indicates that, for the 20 highest air 
emission sources, local emissions are significantly related to local 
blood lead levels.\162\ We are aware of no studies evaluating blood 
lead levels among people who live in close proximity to airports with 
piston-engine activity or those for whom lead emissions from piston 
engines may elevate their exposure via other exposure pathways. As 
noted in Section II.B.2, the current evidence indicates that the slope 
for

[[Page 22461]]

lead effects on IQ is nonlinear and is steeper at lower blood lead 
levels, such that each [mu]g/dL increase in blood lead may have a 
greater effect on IQ at lower blood lead levels (e.g., below 10 [mu]g/
dL) than at higher levels (AQCD for Lead, Section 6.2.13; pp. 8-63 to 
8-64; Figure 8-7). We are therefore seeking comment and information 
regarding blood lead concentrations in children living near airports 
and the extent to which these emissions cause or contribute to any 
increases in blood lead levels.
---------------------------------------------------------------------------

    \162\ U.S. Environmental Protection Agency (2007) Pilot Study of 
Targeting Elevated Blood Lead Levels in Children (Draft Final 
Report). Washington DC: U.S. EPA Office of Pollution Prevention and 
Toxics. http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=195303.
---------------------------------------------------------------------------

2. Children Attending School Near Airports
    As noted in Section II.B.2 of this ANPR, while adults are 
susceptible to lead effects at lower blood lead levels than previously 
understood (e.g., AQCD for Lead, p. 8-25), there is general consensus 
that the developing nervous system in children is among the, if not 
the, most sensitive health endpoints. Also, as noted in Section II.B.3, 
while children are considered to be at a period of maximum exposure 
around 18-27 months, the current evidence has found even stronger 
associations between blood lead levels at school age and IQ at school 
age. The evidence ``supports the idea that lead exposure continues to 
be toxic to children as they reach school age, and [does] not lend 
support to the interpretation that all the damage is done by the time 
the child reaches 2 to 3 years of age'' (AQCD for Lead, Section 
6.2.12). Accordingly, school-age children are an at-risk population for 
lead exposures. This section discusses potential exposures of children 
at school to lead associated with piston-engine aircraft.
    During the school year, students spend many hours a day at school, 
which usually includes time on school playgrounds and on school 
athletic fields. Those children attending schools in close proximity to 
piston-engine activity may have increased exposure to lead. Using data 
from the U.S. Department of Education's National Center for Education 
Statistics, EPA calculated that there are 8,637 schools located within 
one kilometer of the centroid of an airport in the U.S., at which over 
3 million children are in attendance (Table 1).163 164 These 
children represent 6% of the total U.S. student population.
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    \163\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to 
docket EPA-HQ-OAR-2007-0294, titled, ``Identification of Schools 
Within 1 km of U.S Airport Facilities.''
    \164\ Public School Data available for 2006-2007: http://nces.ed.gov/ccd/bat/; Private School Data available for 2007-2008: 
http://nces.ed.gov/surveys/pss/pssdata.asp.

   Table 1--Numbers of Public and Private Schools and School Children
  Attending Schools Located Within One Kilometer of the Centroid of an
                Airport Servicing Piston-engine Aircraft
------------------------------------------------------------------------
                                                             Number of
                                             Number of     students who
                                          schools within  attend schools
                                            1 km of an    within 1 km of
                                              airport       an airport
------------------------------------------------------------------------
Private Schools.........................           2,185         420,824
Public Schools..........................           6,452       2,869,939
                                         -------------------------------
    All Schools.........................           8,637       3,290,763
------------------------------------------------------------------------

    Section II.B.1 notes that children in poverty and black, non-
Hispanic children have notably higher blood lead levels than do 
economically well-off children and white children, in general. To 
evaluate potential ethnic and economic disparities among children 
attending schools close to airports compared with the general 
population, we used data from the Department of Education that provides 
this information. These data indicate that minorities are 
overrepresented at schools that are located within one kilometer from 
the centroid of an airport. For example, Hispanic students represent 
23% of students at schools located within one kilometer of an airport, 
whereas Hispanic students represent 19% of students in all U.S. schools 
(Table 2). Black students represent 18% of students at schools located 
within one kilometer of an airport, whereas black students represent 
16% of the student population in the U.S. (Table 2).

       Table 2--Racial Distribution at Schools Within One Kilometer of the Centroid of an Airport and the Racial Distribution at all U.S. Schools
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             American
                                                          Indian/Alaskan   Asian/Pacific    Black, Non-      Hispanic       White, Non-        Total
                                                              Indian         Islander        Hispanic                        Hispanic        students*
--------------------------------------------------------------------------------------------------------------------------------------------------------
All Schools within 1 km of an       Number..............          46,861         154,408         597,223         764,704       1,646,882       3,290,763
 airport.
                                    Percent.............              1%              5%             18%             23%             50%
All U.S. Schools..................  Number..............         632,237       2,581,822       8,696,565      10,525,763      30,664,231      54,271,986
                                    Percent.............              1%              5%             16%             19%             57%
--------------------------------------------------------------------------------------------------------------------------------------------------------
* This table includes only those children that identify as one of the five races/ethnicities. A small fraction of students identify as mixed race or
  `other' and they are not included here, therefore the percent of students does not total 100%.

    In general, housing and income data suggest that people living in 
close proximity to major transportation sources (i.e., major roadways, 
airports, ports, railyards) are likely to have lower income than the 
general population.\165\ To evaluate the socioeconomic status of 
students who attend schools near airports, EPA evaluated the number of 
students who are eligible for the U.S. Department of Agriculture's free 
or reduced school lunch program. Children

[[Page 22462]]

from families with incomes at or below 130 percent of the poverty level 
are eligible for free meals. Those with incomes between 130 percent and 
185 percent of the poverty level are eligible for reduced-price 
meals.\166\ Free and reduced lunch eligibility is only tracked by the 
U.S. Department of Education's National Center for Education Statistics 
for students who attend public schools. At public schools that are 
located within one kilometer of the centroid of an airport, 47% of 
students are eligible for either free or reduced lunches, whereas 
nationally, 41% of students at public schools are eligible for either 
free or reduced lunches. As this analysis demonstrates, those living in 
the vicinity of airports are more likely to be low-income households 
and minority residents.
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    \165\ U.S. Environmental Protection Agency (2007) Regulatory 
Impact Analysis for the Regulation to Control Hazardous Air 
Pollutant Emissions from Mobile Sources. Chapter 3, p. 3-122.
    \166\ United States Department of Agriculture: Food and 
Nutrition Service, National School Lunch Program Fact Sheet. 
Obtained from: http://www.fns.usda.gov/cnd/Lunch/AboutLunch/NSLPFactSheet.pdf, August 3, 2009. For the period July 1, 2008, 
through June 30, 2009, 130 percent of the poverty level is $27,560 
for a family of four; 185 percent is $39,220.
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    We are aware of no studies evaluating blood lead levels among 
children attending school in close proximity to airports with piston-
engine activity. We are seeking comment and information regarding blood 
lead concentrations in children who attend schools in close proximity 
to airports and the extent to which these emissions cause or contribute 
to any increases in blood lead levels.
3. Agricultural Activities
    Piston-engine aircraft are used in a variety of agricultural 
activities that may introduce lead into the human diet as well as 
contribute to lead in the environment. The FAA conducts the General 
Aviation and Air Taxi Activity (GAATA) Survey annually to obtain 
information on the general aviation and air taxi fleet, the number of 
hours flown, and the reasons people use general aviation and air taxi 
aircraft.167 168 According to the results of the 2007 GAATA 
Survey (the most recent), aerial application in agriculture and 
forestry represented 5% of all hours flown by general aviation aircraft 
in 2007. Of the total aerial application hours flown in 2007 (1.41 
million hours), 60% of the hours were flown by piston-engine aircraft. 
Aerial application activity includes crop and timber production, which 
involve fertilizer and pesticide application and seeding cropland. The 
National Agricultural Aviation Association estimates that there are 
approximately 3,200 aerial application professional operators and 
pilots in the United States.\169\
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    \167\ The FAA GAATA is a database collected from surveys of 
pilots flying aircraft used for general aviation and air taxi 
activity. For more information on the GAATA, see Appendix A at 
http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/.
    \168\ National Agricultural Aviation Association: ``Help the 
Aerial Application Industry by completing the 2008 General Aviation 
Activity Survey.'' Retrieved from: http://www.agaviation.org/2008%20GenAvnSurvey.htm on August 13, 2009.
    \169\ National Agricultural Aviation Association: ``History.'' 
Retrieved from: http://www.agaviation.org/history.htm on August 13, 
2009.
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    As discussed in Section II.C.1, surface deposition of lead onto 
plants may represent a significant contribution to the total lead in 
and on the plant. Lead halides, the primary form of lead emitted by 
engines operating on leaded fuel, are slightly water soluble. They 
therefore may be more readily absorbed by plants than other forms of 
inorganic lead. Atmospheric deposition of lead also contributes to lead 
in vegetation as a result of contact with above-ground portions of the 
plant (AQCD for Lead, pp. 7-9 and AXZ7-39; USEPA, 1986, Sections 6.5.3 
and 7.2.2.2.1). Livestock may subsequently be exposed to lead in 
vegetation (e.g., grasses and silage) and in surface soils via 
incidental ingestion of soil while grazing (USEPA 1986, Section 
7.2.2.2.2).\170\ The lead concentration of plants ingested by animals 
is primarily a result of atmospheric deposition of lead particles onto 
plant surfaces rather than the uptake of soil lead through plant roots. 
Some of the highest levels of lead exposure among livestock have been 
attributed to grazing near major sources such as smelters (AQCD for 
Lead, Section 2.3.8). Atmospheric deposition is estimated to comprise a 
significant proportion of lead in food (AQCD for Lead, p. 3-48) and 
dietary intake may be a predominant source of lead exposure among 
adults (greater than consumption of water and beverages or inhalation 
(73 FR 66971)).
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    \170\ U.S. Environmental Protection Agency (1986) Air Quality 
Criteria for Lead. Research Triangle Park, NC: Office of Health and 
Environmental Assessment, Environmental Criteria and Assessment 
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from: 
NTIS, Springfield, VA; PB87-142378.
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    Depending on wind conditions, an aircraft involved in aerial 
application may fly only 4 inches to 12 feet above the 
crops.171 172 173 The low flying height is needed to 
minimize the drift of the fertilizer and pesticide particles away from 
their intended target. An unintended consequence of this practice is 
that exhaust emissions of lead have a substantially increased potential 
for directly depositing on vegetation and surrounding soil. We have not 
identified any data or analyses regarding the contribution of piston-
engine aircraft lead emissions to lead concentrations in or on plant 
tissues, in livestock or the dose that this might deliver to the human 
population. We are seeking comments on the potential significance of 
this exposure pathway.
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    \171\ Xiong, Chao. (9-23-2007) ``Future for Crop Dusters is up 
in the Air''. The Star Tribune. Retrieved on August 12, 2009 from: 
http://www.startribune.com/local/11606661.html.
    \172\ Harpole, T. (3-1-2007) ``That Old-Time Profession'' Air & 
Space Magazine. Retrieved on August 12, 2009 from: http://www.airspacemag.com/history-of-flight/old_time_profession.html.
    \173\ Petersen, R. ``So you want to be a spray pilot''. AgAir 
Update. Retrieved on October 9, 2009 from: http://www.agairupdate.com/aau/wannabe/pilot.html.
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4. Pilots, Student-Trainees, Passengers
    Pilots, student-trainees, and passengers are all potentially 
exposed to lead emissions from piston-engine aircraft that use leaded 
avgas. General aviation passengers and pilots access their aircraft in 
areas that are typically in close proximity to runways. Therefore, 
these individuals walk near and breathe the air near locations where 
aircraft are idling, conducting run-up checks, taxiing, taking off, and 
landing.
    In the U.S., general aviation aircraft fly over 27 million hours 
and carry 166 million passengers annually.\174\ Approximately 36 
percent of the hours flown by general aviation are for personal 
transportation, 19 percent are instructional flight hours, 11 percent 
are corporate flight hours, 11 percent are for business, eight percent 
are air taxi and air tours and the remainder include hours spent in 
other applications such as aerial observation and aerial 
application.\175\ According to the 2008 General Aviation Statistical 
Databook & Industry Outlook report by the General Aviation 
Manufacturers Association (GAMA) there were 578,541 pilots in the 
United States in 2008.\176\ Among the pilot population, 75,382 were 
student pilots, comprising 13% of the total pilot population. The 
majority of initial pilot training is conducted in piston-engine 
aircraft.\177\ There is no age minimum for

[[Page 22463]]

pilots to begin taking flying lessons.\178\ The minimum age for 
conducting a solo flight is 16 years and a pilot certificate cannot be 
issued until 17 years of age. According to the 2008 General Aviation 
Statistical Databook & Industry Outlook report by the GAMA, there are 
190 student pilots in the 14-15 year old age group and 11,562 student 
pilots in the 16-19 years old age group. GAMA reports that in 2008 
there are 3,846 private pilots in the 16-19 years old age group. 
According to the FAA there are more than 500 flight training 
schools.179 180 The requirement for a private pilot 
certificate is 40 hours in a non-approved school, and 35 hours in an 
approved school. However, most people obtain 60 to 75 hours of training 
before earning their pilot certificate.
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    \174\ General Aviation Manufacturers Association (2008) General 
Aviation Statistical Databook and Industry Outlook. Available at: 
http://www.gama.aero/files/2008_general_aviation_statistical_databook_indust_499b0dc37b.pdf.
    \175\ General Accounting Office Report to Congressional 
Requesters (2001) General Aviation Status of the Industry, Related 
Infrastructure, and Safety Issues. GAO-01-916.
    \176\ GAMA 2008 General Aviation Statistical Databook & Industry 
Outlook report. Retrieved on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook_indust_499b0dc37b.pdf.
    \177\ See http://flighttraining.aopa.org/.
    \178\ Federal Aviation Administration (FAA). ``Become a Pilot--
Student Pilot's Certificate Requirements.'' Retrieved on August 17, 
2009 from: http://www.faa.gov/pilots/become/student_cert/.
    \179\ Federal Aviation Administration (FAA). ``Types of Pilot 
Schools & Choosing a Pilot School''. Retrieved on August 17, 2009 
from: http://www.faa.gov/training_testing/training/pilot_schools/.
    \180\ Federal Aviation Administration (FAA). ``Pilot Schools--
Search''. Retrieved on August 17, 2009 from: http://av-info.faa.gov/PilotSchool.asp.
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    The general public for whom flying is a recreational activity may 
be the most highly exposed population to lead emissions from piston-
engine activity. In addition to their inhalation exposure to engine 
exhaust emissions, pilots can be exposed to evaporative emissions of 
TEL during aircraft fueling, and fuel sump checks during preflight 
inspections.
5. Bioaccumulation of Lead in Aquatic Organisms
    As discussed in Section II.C.2 of this ANPR, lead bioaccumulates in 
the tissues of aquatic organisms through ingestion of food and water. 
Because of the potential for significant deposition of lead compounds 
to water bodies, EPA researches and reports on the atmospheric 
deposition of lead compounds to the Great Waters (the Great Waters 
include the Great Lakes, Lake Champlain, Chesapeake Bay and many U.S. 
coastal estuaries).\181\ Alkyl lead, in particular, has been identified 
by EPA as a Level I Persistent, Bioaccumulative, and Toxic (PBT) 
pollutant. Level I substances are targeted for virtual elimination 
through pollution prevention and other incentive-based actions that 
phase out their use, generation or release in a cost-effective manner 
within the most expedient timeframe. In 2002, EPA issued the PBT 
National Action Plan for Alkyl-lead to promote further voluntary 
reductions of use and exposure to alkyl lead compounds, including 
leaded avgas.\182\
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    \181\ U.S. Environmental Protection Agency, ``The Great Waters 
Program.'' Retrieved on August 17, 2009 from: http://www.epa.gov/air/oaqps/gr8water/ gr8water/.
    \182\ U.S. Environmental Protection Agency Persistent, 
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT 
national action plan for alkyl-Pb. Washington, DC. Available online 
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
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    We are interested in the potential for lead emissions from piston-
engine aircraft to be a source of lead pollution to aquatic organisms. 
Among the approximately 20,000 airport facilities in the United States 
there are 448 seaplane facilities. Landing and take-off activity by 
aircraft at these facilities provides a direct pathway for emission of 
organic and inorganic lead to the air near/above inland waters and 
ocean seaports where these aircraft operate. In addition to seaplane 
facilities, many airports and heliports are located very close to 
rivers, lakes and streams, which can provide a direct pathway for 
emission of organic and inorganic lead to the air near/above inland 
waters. Lead emissions from seaplane facilities as well as airports and 
heliports near water bodies can enter the aquatic ecosystem by either 
deposition from ambient air or runoff of lead deposited to surface 
soils. As noted in Section IV.A, lead halides (the primary form of lead 
emitted by engines operating on leaded fuel) are slightly water-soluble 
and may be more readily dissolved into water than other inorganic forms 
of lead.
    The EPA Office of Water maintains a database of the National 
Listing of Fish Advisories (NLFA) which is made available on the 
Internet to provide information regarding locally-issued fish 
advisories and safe eating guidelines.\183\ States, territories, and 
Tribes (collectively referred to here as ``States'') provide this 
information to EPA every year. The most recent year for which data are 
available is 2008. States provide information regarding contaminant 
levels of bioaccumulative toxins measured in fish including lead, 
mercury, polychlorinated biphenyls (PCBs) and dioxin. Based on these 
data states issue fish consumption advisories that provide information 
regarding water bodies for which fish tissue concentrations of these 
pollutants are found by the State criteria to be safe or unsafe for 
consumption. The EPA recommends that if fish are detected as having any 
measureable level of accumulated lead in their tissues that this is 
cause for concern for all consumers, but especially for children and 
pregnant or nursing women, and that issuing an advisory is prudent.
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    \183\ U.S. Environmental Protection Agency, ``The National 
Listing of Fish Advisories.'' Retrieved on August 17, 2009 from: 
http://www.epa.gov/waterscience/fish/advisories/.
---------------------------------------------------------------------------

    The 2008 NLFA database includes data on lead concentrations in over 
23,000 fish from over 1,000 lakes and streams. Among these fish, lead 
concentrations were above the analytical detection limit in 1,000 fish 
samples \184\ and among the fish in which measureable lead 
concentrations were reported, the concentrations of lead ranged from 5 
ppb to 60,400 ppb.\185\ States do not provide information regarding the 
source of contamination in water bodies where fish tissue 
concentrations of lead are above detection limits. Lead concentrations 
in fish tissue samples declined from mean concentrations of 0.28 ppm in 
1976 to 0.11 ppm in 1984.\186\ The decrease in mean lead concentrations 
was attributed primarily to reductions in the lead content of motor 
vehicle gasoline. Sources of contamination of lead to waterways 
frequently noted include lead gunshot, lead sinkers, and Superfund 
sites.\187\ Lead emissions from piston-engine aircraft may contribute 
to fish tissue lead concentrations in water bodies that are in close 
proximity to piston-engine aircraft activity. In one case, a State 
reported lead contaminated fish in a lake on airport property. Piston-
engine aircraft emissions of lead also have the potential to contribute 
to fish tissue lead concentrations at water bodies throughout the U.S. 
due to the emission of lead in-flight. These in-flight emissions are 
greatly dispersed in the environment and have been providing a source 
of lead to the environment for over 80 years.
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    \184\ In some instances States supply individual fish tissue 
sample results and in some instances States supply averages of 
multiple fish tissue sample results.
    \185\ State-specific fish advisories for lead can be downloaded 
from: http://oaspub.epa.gov/nlfwa/nlfwa.bld_qry?p_type=advrpt&p_loc=on.
    \186\ U.S. Environmental Protection Agency (2000) Guidance for 
Assessing Chemical Contaminant Data for Use in Fish Advisories. 
Volume 1: Fish Sampling and Analysis. EPA 823-B-00-007. p. 4-59. 
Available online at: http://www.epa.gov/waterscience/fish/advice/volume1/index.html.
    \187\ U.S. Environmental Protection Agency, ``Lead Fishing.''. 
Retrieved on August 17, 2009 from: http://www.epa.gov/owow/fish/animals.html.
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    The Fond du Lac Band of Lake Superior Chippewa, the Leech Lake Band 
of Ojibwe and the Mille Lacs Band of Ojibwe submitted comments to the 
Lead NAAQS docket noting the importance of fish consumption in their 
diet.\188\ The Fond du Lac Band of Lake

[[Page 22464]]

Superior Chippewa also noted in their comments, ``As a reservation with 
a municipal airport within its exterior boundaries with two schools and 
Tribal housing in close proximity to the airport (one half mile), 
leaded aircraft fuel is a concern.'' The Leech Lake Band of Ojibwe 
noted in their comments, ``Along with the concerns over the emission 
inventory, the Tribes have great concern regarding the amount of lead 
from ``small'' prop engine airports. On or very near the Leech Lake 
Reservation there are seven prop plane airports with many private air 
strips scattered throughout the area.'' EPA is requesting comment on 
any information regarding the potential impact of lead emissions from 
piston-engine aircraft on aquatic environments.
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    \188\ See Docket ID Number EPA-HQ-OAR-2006-0735. The Tribes that 
submitted comments were: The Bad River Band of Lake Superior Tribe 
of Chippewa Indians, The Quapaw Tribe of Oklahoma, The Leech Lake 
Band of Ojibwe, The Lone Pine Paiute-Shoshone Reservation, The Fond 
du Lac Band of Lake Superior Chippewa, and The Mille Lacs Band of 
Ojibwe.
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B. Related Exposures of Concern

    While the subject of this ANPR is focused on the emissions of lead 
from piston-engine aircraft, the use of tetraethyl lead in fuel 
contributes to additional public health and welfare issues that are 
also of concern to the Agency. Among these issues are: (1) The 
contribution of lead emissions to ambient PM, especially in areas in 
nonattainment with the PM2.5 NAAQS; (2) the emissions of 
ethylene dibromide to the environment; and (3) the evaporative 
emissions of tetraethyl lead.
1. Lead Contribution to Ambient Particulate Matter
    As discussed in Section IV.A of this ANPR, lead emitted by piston 
engines is expected to be predominantly in the particle phase and will 
contribute to ambient PM. There are two U.S. National Ambient Air 
Quality Standards (NAAQS) for PM2.5: an annual standard (15 
[mu]g/m\3\) and a 24-hour standard (35 [mu]g/m\3\). As of March 4, 2009 
there are 39 1997 PM2.5 nonattainment areas. Area 
designations for the 2006 24-hour PM2.5 NAAQS were 
promulgated in 2009 for 31 areas.\189\ All of these nonattainment areas 
have at least one airport servicing aircraft using leaded avgas and 
most nonattainment areas have several airport facilities. The Los 
Angeles-South Coast Air Basin has 343 airport facilities which have a 
cumulative lead inventory of 15.0 tons. The contribution of PM-lead to 
these nonattainment areas ranges from 0.001 to 0.7% of the mobile 
source PM2.5 inventory in these areas. In each of four areas 
designated as nonattainment with the PM2.5 annual standard, 
there is at least one lead monitor at which design values for 2006-2008 
are greater than the 2008 Lead NAAQS and two of these counties have 
PM2.5 concentrations exceeding the 24-hour PM2.5 
NAAQS. Reductions in lead emissions in these counties would help bring 
the area into attainment.
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    \189\ http://www.epa.gov/pmdesignations/.
---------------------------------------------------------------------------

2. Ethylene Dibromide
    As noted in Section IV.A, ethylene dibromide (1,2-dibromoethane) is 
added to leaded avgas to scavenge lead in order to prevent the 
deposition of lead oxide to valves and spark plugs. Emissions of 
ethylene dibromide are a concern to the EPA. Ethylene dibromide is 
classified in EPA's Integrated Risk Information System database as 
likely to be carcinogenic to humans, and a number of chronic noncancer 
effects have been observed in animals and humans exposed to ethylene 
dibromide by inhalation and ingestion.\190\ EPA developed an inhalation 
reference concentration, ingestion dose and cancer unit risk estimates 
for inhalation and ingestion of ethylene dibromide.\191\ Evidence of 
nasal tumors, hemangiosarcomas and mesotheliomas in rodents was used by 
EPA to develop inhalation unit risk estimates (central tendency 
estimates and 95% upper bound estimates) of 3 x 10-\4\ to 6 
x 10-\4\ per [mu]g/m\3\. Evidence of forestomach tumors, 
hemangiosarcomas, thyroid follicular cell adenomas or carcinomas was 
used by EPA to develop drinking water unit risk estimates (central 
tendency estimates and 95% upper bound estimates) of 3 x 
10-\5\ to 6 x 10-\5\ per [mu]g/L assuming 
consumption of 2 L of water per day by a 70 kg human. EPA developed a 
reference concentration for chronic inhalation of 9 [mu]g/m\3\ based on 
the critical effect of nasal inflammation and a reference dose for 
chronic ingestion of 9 [mu]g per kg per day based on the critical 
effects of testicular atrophy, liver peliosis, and adrenal cortical 
degeneration. The National Toxicology Program listed ethylene dibromide 
as ``reasonably anticipated to be a human carcinogen'' in the Eleventh 
Report on Carcinogens in 2005.\192\ The International Agency for 
Research on Cancer (IARC) has classified ethylene dibromide as a Group 
2A carcinogen: probably carcinogenic to humans.-
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    \190\ U.S. Environmental Protection Agency (2004) Integrated 
Risk Information System (IRIS), IRIS Summary for 1,2-dibromoethane 
CASRN 106-93-4. Available online at: http://www.epa.gov/ncea/iris/subst/0361.htm.
    \191\ U.S. Environmental Protection Agency (2004) Integrated 
Risk Information System (IRIS), Toxicological Review of 1,2-
dibromoethane in support of summary information on the Integrated 
Risk Information System. Available online at: http://www.epa.gov/ncea/iris/toxreviews/0361tr.pdf.
    \192\ National Toxicology Program (NTP) (2005) 11th Report on 
Carcinogens. Public Health Service, U.S. Department of Health and 
Human Services, Research Triangle Park, NC. Available from: http://ntp-server.niehs.nih.gov.
---------------------------------------------------------------------------

    In the additive package used to dose fuel with lead, ethylene 
dibromide is added to achieve a lead-to-bromine atom ratio of 1:2 and a 
bromine-to-lead weight ratio of 1:2.\193\ The concentration of ethylene 
dibromide in leaded avgas is listed as less than 4 milliliters per 
gallon (<9 grams per gallon).\194\ Since ethylene dibromide was 
measured in the exhaust and evaporative emissions from light-duty 
vehicles in the U.S. when they were operated on leaded fuel containing 
ethylene dibromide we anticipate piston-engine aircraft are currently a 
source of ethylene dibromide to air.\195\ Measurements of ethylene 
dibromide have not been made that would allow estimation of the exhaust 
and evaporative emissions from piston-engine aircraft as well as the 
emissions associated with refueling and pre-flight fuel checks.
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    \193\ Thomas VM; Bedford JA; Cicerone RJ. (1997) Bromine 
emissions from leaded gasoline. Geophys Res Letters 24(11):1371-
1374.
    \194\ Chevron Material Safety Data Sheet for aviation gasoline. 
Available online at: http://www.chevronglobalaviation.com/docs/aviation_gas.doc.
    \195\ Sigsby, J.E.; Dropkin, D.L.; Bradow, R.L.; Lang, J.M. 
(1982) Automotive Emissions of Ethylene Dibromide. SAE Technical 
Paper Series 820786.
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    In addition to contributing to ambient concentrations, ethylene 
dibromide may also enter underground aquifers via leaking underground 
storage tanks or fuel spills. Studies demonstrate that ethylene 
dibromide may persist for long periods of time in certain groundwater 
environments.\196\ The EPA established a Maximum Concentration Level 
(MCL) of 0.05 [mu]g/L for ethylene dibromide, which is 100-fold lower 
than the MCL for benzene and 300-fold lower than the MCL for lead. The 
MCL is the highest level of a contaminant that is allowed in drinking 
water and is an enforceable drinking water standard.\197\
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    \196\ U.S. Environmental Protection Agency Office of Research 
and Development (2008) Natural Attenuation of the Lead Scavengers 
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor 
Fuel Release Sites and Implications for Risk Management, Chapter 2. 
EPA 600/R-08/107. Available online at: http://www.epa.gov/ada.
    \197\ U.S. Environmental Protection Agency, ``Drinking Water 
Contaminants'' Available online at: http://www.epa.gov/safewater/contaminants/index.html.
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    The EPA Office of Underground Storage Tanks (OUST) and Office of 
Research and Development's National Risk Management Research Laboratory 
(NRMRL) in association with the Association of State and Territorial

[[Page 22465]]

Solid Waste Management Officials (ATSWMO) have formed a team to 
evaluate the potential for public health and welfare effects 
attributable to ethylene dibromide from past or present fuel leaks and 
spills.\198\ Among the goals of the EPA/ATSWMO team is to develop 
information on the distribution of ethylene dibromide in groundwater at 
leaking underground storage tank sites in States that do not routinely 
monitor this contaminant. Water samples for this study were provided by 
State agencies to EPA between October 2005 and July 2007. Of the 802 
groundwater samples provided from 102 sites, ethylene dibromide was 
detected in 54 samples, 43 of which had ethylene dibromide 
concentrations above the MCL.\199\ These sites did not include analysis 
of groundwater at airports.
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    \198\ U.S. Environmental Protection Agency Office of Research 
and Development (2008) Natural Attenuation of the Lead Scavengers 
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor 
Fuel Release Sites and Implications for Risk Management. p.3. EPA 
600/R-08/107. Available online at: http://www.epa.gov/ada.
    \199\ U.S. Environmental Protection Agency Office of Research 
and Development (2008) Natural Attenuation of the Lead Scavengers 
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor 
Fuel Release Sites and Implications for Risk Management. p.4. EPA 
600/R-08/107. Available online at: http://www.epa.gov/ada.
---------------------------------------------------------------------------

    While not the focus of this ANPR, ethylene dibromide exposure from 
inhalation or ingestion pathways is an ongoing concern for EPA, and 
reduction in the use of leaded gasoline containing ethylene dibromide 
may reduce exposure and risk to public health and welfare from ethylene 
dibromide.
3. Non-Exhaust Exposure to Tetraethyl Lead
    Tetraethyl lead is a volatile component of leaded avgas. The 
largest source of tetraethyl lead exposure is expected to originate 
from evaporative emissions associated with fuel production, fuel 
distribution, aircraft refueling, pre-flight fuel checks, accidental 
spills, and fuel tank venting. Pilots check fuel for contaminants by 
draining a small amount of fuel from each tank sump before flight and 
after refueling. This fuel is frequently deposited onto the tarmac 
after the fuel check. EPA is interested in data regarding this practice 
and any estimates of lead emitted to the air by evaporation of the 
alkyl lead in the fuel deposited on the tarmac. Alkyl lead becomes 
oxidized in the atmosphere by direct photolysis, reaction with ozone, 
and by reaction with hydroxyl compounds. Therefore, depending on 
ambient conditions, alkyl lead may exist in the atmosphere for hours to 
days.
    Pilots, aviation fuel attendants and mechanics are likely to be 
among the most highly exposed population to alkyl lead. These 
populations are at risk due to both inhalation and possible dermal 
exposure. Absorption of inhaled alkyl lead into the bloodstream is 
higher than that for inorganic lead compounds which are generally in 
particulate form (AQCD for Lead, Section 4.2.1). In addition to 
exposure to lead in the exhaust emissions from piston-engine aircraft, 
the PBT National Action Plan for Alkyl-lead \200\ noted that aviation 
fuel attendants and mechanics are potentially exposed to alkyl lead 
emissions due to inhalation of alkyl lead compounds released to the air 
during fueling, via evaporative emissions from spills, or via 
evaporative emissions from unused gasoline remaining in the engine or 
fuel tanks. Further, these populations are also at risk because of 
possible dermal absorption of gasoline containing alkyl lead compounds. 
Due to the lipophilic nature of alkyl lead and its ability to permeate 
biological membranes, alkyl lead is absorbed rapidly and extensively 
through the skin (AQCD for Lead, page 4-12). In addition to direct 
human exposure, runoff and deposition of alkyl lead to waterways would 
increase the amount of lead available for uptake by aquatic plants and 
animals (see Section V.A.7 of this ANPR for more information).
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    \200\ U.S. Environmental Protection Agency Persistent, 
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT 
national action plan for alkyl-Pb. Washington, DC. Page 14. 
Available online at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf
---------------------------------------------------------------------------

VI. Additional Information Available for the NPRM To Evaluate the 
Potential for Public Health and Welfare Impacts and Considerations 
Regarding Engine Emission Standards

    As noted in the Overview section of this ANPR, in this action we 
are describing information currently available and information being 
collected that will be used by the Administrator to subsequently 
exercise her judgment regarding whether aircraft lead emissions from 
avgas use cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health or welfare. These additional data 
will come from lead monitoring being planned to satisfy requirements of 
the Lead NAAQS, air quality modeling planned at EPA that is described 
below and any information submitted to EPA during the comment period 
for this ANPR.

A. The Lead NAAQS and Lead Emissions From Piston-Engine Aircraft

    On November 12, 2008, when EPA promulgated revisions to the Lead 
NAAQS, EPA also adopted revisions to ambient air monitoring 
requirements for lead, described the approach for implementing the 
revised standards, and provided an implementation timeline. We describe 
each of these activities as well as more recent activities below. This 
section also discusses the most current information available regarding 
how implementation of the Lead NAAQS may provide additional data on the 
potential for lead emissions from piston-engine aircraft to cause or 
contribute to ambient air concentrations that exceed the 2008 Lead 
NAAQS.
    Acknowledging that the existing monitoring network for lead is not 
sufficient to determine whether many areas of the country would meet 
the 2008 Lead NAAQS, the EPA re-designed the nation's lead monitoring 
network to allow assessment of compliance with the revised lead 
standard. Lead monitoring requirements promulgated in 2008 stipulate 
that, at a minimum, monitoring agencies must place monitors at maximum 
impact areas where lead emissions are greater than or equal to one ton 
or more per year. We refer to these monitors as source-oriented 
monitors. EPA Regional Administrators may waive the source-oriented 
monitoring requirements if the monitoring agency can demonstrate that 
emissions from the source will not contribute to maximum air lead 
concentrations greater than 50 percent of the revised standard, or 
0.075 ug/m\3\. EPA estimated that approximately 135 facilities emit 
lead at levels over the one ton emission threshold, making them subject 
to the lead monitoring requirements. Lead monitors are operating at a 
small number of these sources (described in Section VI.A.2 below). For 
the remainder, source-oriented monitors are to be operational by 
January 1, 2010.
    EPA also required monitors to be operated in each of the 101 urban 
areas with populations greater than 500,000 in order to gather 
information on the general population's exposure to lead in air. We 
refer to these monitors as population-oriented monitors.
    Following promulgation of the 2008 Lead NAAQS and monitoring 
requirements, the Natural Resources Defense Council, the Missouri 
Coalition for the Environment Foundation, Physicians for Social 
Responsibility, and the Coalition to End Childhood Lead Poisoning 
(Petitioners) petitioned

[[Page 22466]]

EPA for reconsideration of the lead emission rate at which we required 
monitoring (the ``emission threshold,'' currently 1.0 tpy).\201\ EPA 
granted the petition to reconsider aspects of the monitoring 
requirements and proposed revisions to lead ambient air monitoring 
requirements in December 2009 (74 FR 69050).
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    \201\ The petition is available at: http://www.epa.gov/air/lead/pdfs/OAR.09.000.7687.pdf.
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    Also as part of promulgating the 2008 Lead NAAQS, EPA described the 
approach for implementing the revised standards and provided an 
implementation timeline. EPA will use county boundaries as the 
presumptive boundaries for nonattainment areas, and adjustments to 
boundaries will be made on case-by-case bases. States in which there is 
sufficient monitoring data made recommendations for areas to be 
designated attainment, nonattainment, or unclassifiable in October 
2009. States update their recommendations to EPA in October 2010 using 
any additional monitoring data available from the increased source-
oriented monitoring network described above. Final designations of all 
attainment, nonattainment and unclassifiable areas will be effective no 
later than January 2012. Where data are sufficient from the currently 
existing lead monitoring network, we expect that initial designations 
will be effective January 2011. States are directed to submit State 
Implementation Plans (SIPs) no later than eighteen months after 
designation, outlining how they will reduce pollution to meet the lead 
standards. States are required to attain the standards no later than 
five years after designation. Additional information regarding the lead 
standard implementation is available at http://www.epa.gov/air/lead/actions.html and in the 2008 Lead NAAQS (73 FR 67030-67043).
1. Monitoring Lead at Airports To Evaluate Ambient Concentrations to 
Which Lead Emissions From Piston-Engine Aircraft Contribute
    Among the estimated 135 source-oriented lead monitoring sites, 
there are four airports where we expect lead monitoring to begin in 
January 2010. These airports are the Van Nuys Airport in Van Nuys, CA; 
the Phoenix Deer Valley Airport in Phoenix, AZ; the Centennial Airport 
in Englewood, CO; and the Daytona Beach International Airport in 
Daytona Beach, FL. In each of these areas, we will, as data becomes 
available, evaluate the impact of lead emissions from piston-engine 
aircraft on air quality.
2. Evaluating the Contribution of Lead Emissions From Piston-Engine 
Aircraft to Areas Approaching or Exceeding the Lead NAAQS
    In this section we discuss available information and information 
that will become available in 2010 that can be used to evaluate the 
potential for lead emissions from piston-engine aircraft to contribute 
to ambient concentrations in areas exceeding the Lead NAAQS. This 
evaluation may include the following: (1) Areas currently out of 
attainment or designated as maintenance with the 1978 Lead NAAQS; (2) 
areas with current lead monitors that are out of attainment with the 
2008 Lead NAAQS; and (3) locations that will have new lead monitors to 
meet the 2008 Lead NAAQS source-oriented monitoring requirements. In 
each of these areas, we will, as data become available, evaluate the 
contribution of lead emissions from piston-engine aircraft to lead 
inventories and air quality.
    The EPA is retaining the 1978 Lead NAAQS until one year after 
designations for the 2008 Lead NAAQS, except in current nonattainment 
areas. In those areas, EPA will retain the 1978 standard until the area 
submits, and EPA approves, attainment and/or maintenance demonstrations 
for the new standards. Only two areas, East Helena, MT (including Lewis 
and Clark counties), and part of Jefferson County in Herculaneum, MO, 
are designated nonattainment with the 1978 Lead NAAQS. The industrial 
facility causing nonattainment with the Lead NAAQS in the East Helena 
area closed in 2001. Eleven areas are designated as maintenance areas, 
only three of which currently have lead monitors. These three locations 
(Iron County, MO, Dakota County MN, and Collin County, TX) have lead 
monitors with design value concentrations exceeding the 2008 Lead 
NAAQS. The design value is the highest ``rolling'' three month average 
over a three-year period that is relevant for comparison to the level 
of the 2008 Lead NAAQS.
    Implementation of the 2008 Lead NAAQS is underway, and we have not 
yet designated areas under it. When EPA promulgated the 2008 Lead 
NAAQS, EPA provided a list of 18 counties with design values exceeding 
the 2008 lead standard of 0.15 [micro]g/m\3\. Using more recent data 
from EPA's Air Quality System, there are 14 sites at which design 
values exceed the 2008 Lead NAAQS (Table 3). Over 4.6 million people 
live in the counties where design values are greater than the 2008 Lead 
NAAQS. After EPA designates areas that currently have sufficient lead 
monitoring data, no later than October 15, 2010, we will evaluate the 
contribution of lead emissions from piston-engine aircraft to lead 
inventories in nonattainment, maintenance and in some cases, 
unclassifiable areas, depending on the presence of point sources of 
lead and the status of ambient lead monitoring in those areas.

   Table 3--Counties With Maximum Rolling Quarterly Average Lead Concentrations Exceeding the 2008 Lead NAAQS
----------------------------------------------------------------------------------------------------------------
                                                                                      County       Design value,
                          County, state                             EPA region      population       2006-2008
                                                                                   (2000 Census)   ([mu]g/m\3\)
----------------------------------------------------------------------------------------------------------------
Jefferson, MO...................................................               7         198,099            2.89
Iron, MO........................................................               7          10,697            2.46
Delaware, IN....................................................               5         118,769            2.16
Hillsborough, FL................................................               4         998,948            1.77
Collin, TX......................................................               6         491,675            1.26
Pike, AL........................................................               4          29,605            1.21
Dakota, MN......................................................               5         355,904            0.70
Fulton, OH......................................................               5          42,084            0.69
Berks, PA.......................................................               3         373,638            0.36
Madison, IL.....................................................               5         258,941            0.28
Logan, OH.......................................................               5          46,005            0.27

[[Page 22467]]

 
Sullivan, TN....................................................               4         153,048            0.26
Beaver, PA......................................................               3         181,412            0.20
Cuyahoga, OH....................................................               5       1,393,978            0.17
----------------------------------------------------------------------------------------------------------------

    Lead emissions from piston-engine aircraft operating at airports 
outside nonattainment areas can also contribute to lead measured in the 
nonattainment area. In addition, other sources of lead that do not, by 
themselves, exceed the lead emission monitoring threshold may be 
located near airports. For example, at some airports in the U.S., race 
track venues are located immediately adjacent to runways where piston-
engine aircraft operate. We are seeking information regarding ambient 
concentrations of lead that can result from the combined emissions of 
leaded fuel used in some race vehicles, lead emissions from piston-
engine aircraft and other sources of ambient lead.
    The EPA intends to conduct modeling analyses to evaluate the 
contribution of these lead emissions to nonattainment areas and areas 
that may be approaching nonattainment concentrations. Lead emitted by 
piston-engine aircraft flying through nonattainment areas may also 
contribute to lead measured in the nonattainment area. These emissions 
would be potentially challenging to quantify, although a series of 
scoping analyses could be conducted. We seek comment on characterizing 
the contribution of lead emissions from piston-engine aircraft flying 
through areas that are not attaining the 2008 Lead NAAQS and the 
potential contribution of piston-engine lead emissions that may be 
transported into lead nonattainment areas.
    As noted above, approximately 135 new lead monitors will begin 
collecting ambient lead samples starting in January 2010 in order to 
satisfy the source-oriented monitoring requirements of the 2008 Lead 
NAAQS. In the NPRM we will discuss the potential contribution of lead 
from piston-engine aircraft to these areas where the ambient data 
suggest lead concentrations are close to or exceeding the 2008 Lead 
NAAQS of 0.15 [mu]g/m\3\.

B. Additional Information EPA Is Collecting To Evaluate Ambient Lead 
Concentrations Attributable to Emissions From Piston-Engine Aircraft

    In 2008 EPA initiated a study to provide information regarding the 
local-scale gradient in lead concentrations on- and near airport 
facilities with piston-engine powered aircraft activity.\202\ This 
study focused mainly on developing an approach for modeling lead 
emissions from piston-engine aircraft using the Meteorological Society 
(AMS)/EPA Regulatory Model (AERMOD), and evaluating it using air 
quality measurements. For purposes of local-scale dispersion modeling, 
AERMOD is EPA's preferred model.\203\ The approach developed includes 
apportioning lead emitted during landing and take-off to different 
altitudes in order to characterize emissions during these modes of 
operation in a realistic manner. In addition, this modeling study 
includes analysis of the spatial and temporal emissions from piston-
engine aircraft during the other modes of aircraft operation (e.g., 
taxi, run-up check, take-off, landing). The modeling results include an 
evaluation of the relative contributions of all known sources of lead 
to the local ambient air, including piston-engine aircraft, local 
traffic, resuspended road dust, and industrial sources within 20 km of 
the airport selected for our case study. The EPA study at the Santa 
Monica Airport was recently completed.\204\
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    \202\ U.S. EPA (March 2010) Memorandum from Marion Hoyer to the 
docket EPA-HQ-OAR-2007-0294, titled, ``Work Plan for Air Quality 
Modeling and Monitoring of Lead Emissions from Piston-Engine Powered 
Aircraft.'' Docket number EPA-HQ-OAR-2007-0294.
    \203\ The EPA provides modeling guidance for AERMOD at http://www.epa.gov/ttn/scram/guidanceindex.htm and http://www.epa.gov/scram001/dispersion_prefree.htm#aermod. A post-processor for AERMOD 
that reads model output and calculates rolling 3-month averages for 
the period modeled to provide lead concentrations that can be 
compared with the Lead NAAQS is available online at: http://www.epa.gov/ttn/amtic/files/ambient/pb/leadpost.zip.
    \204\ The report from this study is posted at http://www.epa.gov/otaq/aviation.htm.
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    As part of this work, we collected air, soil and house dust samples 
for lead analysis in order to conduct a model-to-monitor evaluation, 
and to evaluate the potential for lead emissions from piston-engine 
aircraft to create a gradient in air, soil and house dust 
concentrations of lead in proximity to the airport activities.
    We selected the Santa Monica municipal airport for this study 
because of the data available from the monitoring study conducted by 
the SCAQMD in 2005-2007 discussed in Section IV.B of this ANPR. In 
addition, there are no major point sources of lead in close proximity 
to the airport, simplifying the model development and interpretation of 
monitoring results.
    EPA intends to use this modeling approach to evaluate potential for 
exceedance of the Lead NAAQS on airport property and surrounding areas, 
as well as providing an approach to characterize the contribution of 
lead emissions from piston-engine aircraft to areas with ambient lead 
concentrations currently exceeding the 2008 Lead NAAQS. This modeling 
approach will also allow us to quantify the changes in ambient lead 
concentrations following the implementation of different piston-engine 
control strategies. The application of this modeling approach to a 
case-study airport could also be used as input to conduct a risk 
assessment evaluating the potential contribution of lead from piston-
engine emissions on blood lead levels and IQ deficits for those living 
near or attending school near general aviation activity.
    We request comment on all information EPA is collecting to evaluate 
ambient lead concentrations attributable to emissions from piston-
engine aircraft and risk posed by emissions of lead from piston-engine 
aircraft.

C. Considerations Regarding Engine Emission Standards

    A positive endangerment and cause or contribute finding with 
respect to the emissions of lead from general aviation aircraft would 
trigger EPA's duty to set emission standards. In considering emission 
standards, EPA would consider controlling emissions from piston engines 
using aviation gasoline in aircraft. In cooperation with FAA, EPA would 
evaluate the technical feasibility of a possible phase-down or 
elimination of leaded aviation gasoline. One option to consider, for 
example, could be an emissions standard

[[Page 22468]]

(established under 40 CFR 87) that would require all newly-manufactured 
general aviation piston engines to be able to operate with appropriate 
reliability and durability on unleaded aviation gasoline by some future 
date. Such a standard might require that new engines used in aircraft 
would have to receive an FAA type certificate that reflects achievement 
of these requirements under FAA regulations set forth at 14 CFR parts 
33/34.
    Beyond this, EPA recognizes that there is a big challenge in 
dealing with the in-use fleet. Converting in-use aircraft/engines to 
operate on unleaded aviation gasoline would be a significant logistical 
challenge, and in some cases a technical challenge as well. In many 
cases, the implementation of this concept might depend upon efforts and 
actions of aircraft and engine manufacturers in identifying the 
necessary modifications and developing hardware as necessary. Depending 
on timing, these engines might need to be able to operate on either 
leaded or unleaded aviation gasoline, or a blend thereof. EPA 
recognizes that in many cases these modifications could trigger the 
need for FAA regulatory approval of the modifications for both the 
engines and airframes. Given the potentially large number of affected 
aircraft and the potential complexities involved, a program affecting 
in-use aircraft engines would need careful consideration by both EPA 
and FAA and the two agencies would need to work together in considering 
any potential program affecting the in-use fleet.
    EPA requests comment on this outline of approaches for 
transitioning the fleet to unleaded aviation gasoline, as well as 
potential implementation dates, if EPA were to trigger the duty to set 
emission standards. Comment is also requested on how a program could be 
best structured to assure that conversions conducted by engine 
manufacturers (OEMs), independent shops, and in the field by certified 
power plant mechanics are performed to fully meet the intent of a 
possible program without compromising the safety of those aircraft and 
engines. EPA also asks for comment on potential problems with this 
approach including suggested modifications, improvements, or other 
approaches. EPA is requesting comment on potential implications for 
international import and export of piston engines and aviation fuel, as 
well as potential impacts on international transport. Finally, EPA 
requests comment on how market incentives might be developed to 
encourage modification to run on unleaded aviation gasoline as part of 
a regulatory requirement.
    As part of the responses to the Federal Register notice EPA 
published in November 2007 entitled ``Petition Requesting Rulemaking to 
Limit Lead Emissions from General Aviation Aircraft,'' EPA received a 
number of comments addressing both technology and fuel-based options as 
potential measures to reduce or eliminate lead in avgas.\205\ In 
addition to these comments, EPA is aware of completed and ongoing work 
done under the auspices of the Coordinating Research Council and more 
recent viewpoints and efforts put forth by industry trade associations, 
airframe/engine manufacturers, specialty vendors, aviation user groups, 
and other innovators. The work and perspectives of these groups on 
technology and avgas fuel quality options are important, and EPA asks 
for further comment reflecting any new data on technology developments, 
fuel formulation approaches, or other technical viewpoints.
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    \205\ 72 FR 64570 (Nov. 16, 2007); EPA Docket EPA-HQ-OAR-2007-
0294.
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    According to Department of Energy data, annual demand for aviation 
gasoline is very small in comparison to motor gasoline yet its use is 
as geographically widespread. This of course creates challenges for 
supply, distribution, and storage. EPA asks for comment on the avgas 
refining locations and practices, supply (including imports and 
exports, if any), details on distribution to terminals and airports, 
and storage practices for avgas at terminals and airports across the 
country. EPA is also interested in comments on progress and timeframes 
for developing alternatives to current leaded avgas and how these might 
be integrated into the fuel supply and distribution system.

VII. Statutory and Executive Order Reviews

    Under Executive Order 12866, entitled Regulatory Planning and 
Review (58 FR 51735, October 4, 1993), this is a ``significant 
regulatory action'' because of the cross-agency nature of this issue. 
Accordingly, EPA submitted this action to the Office of Management and 
Budget (OMB) for review under Executive Order 12866 and any changes 
made in response to OMB recommendations have been documented in the 
docket for this action. Because this action does not propose or impose 
any requirements, other statutory and Executive Order reviews that 
apply to rulemaking do not apply. Should EPA subsequently determine to 
pursue a rulemaking, EPA will address the statues and Executive Orders 
as applicable to that rulemaking.
    Nevertheless, the Agency welcomes comments and/or information that 
would help the Agency to assess any of the following: Tribal 
implications pursuant to Executive Order 13175, entitled Consultation 
and Coordination with Indian Tribal Governments (65 FR 67249, November 
6, 2000); environmental health or safety effects on children pursuant 
to Executive Order 13045, entitled Protection of Children from 
Environmental Health Risks and Safety Risks (62 FR 19885, April 23, 
1997) and human health or environmental effects on minority or low-
income populations pursuant to Executive Order 12898, entitled Federal 
Actions to Address Environmental Justice in Minority Populations and 
Low-Income Populations (59 FR 7629, February 16, 1994). The Agency will 
consider such comments during the development of any subsequent 
rulemaking.

    Dated: April 20, 2010.
Lisa P. Jackson,
Administrator.
[FR Doc. 2010-9603 Filed 4-27-10; 8:45 am]
BILLING CODE 6560-50-P